Joe Biden has won. Here’s what comes next.

Joe Biden — a former two-term vice president under Barack Obama and 36-year Senate veteran — will be the 46th president of the United States. His running mate, California Sen. Kamala Harris, will become the first woman, first African American, and first Indian American to serve as vice president.

The Democratic nominee is the projected winner in enough states to win 270 electoral votes. The state of Pennsylvania, which Hillary Clinton lost in 2016, was called by our partners at Decision Desk for Biden just before 9 am ET on November 6, clinching the electoral win in a tightly contested vote that drew historic turnout. (For more on how Decision Desk and other outlets call elections, read our explainer here.)

The victory comes as a massive relief to Biden’s supporters after an anxiety-ridden few days during which a record amount of mail-in ballots were tallied. It also serves as a promise — though certainly not a guarantee — that the high-octane drama of the Trump years might finally be coming to an end.

Trump, for his part, has signaled he may not go quietly, calling into question the legitimacy of the late-counted votes that arrived by mail in the states that clinched it for Biden.

For Biden and Harris, the victory marks the end of the campaign — but the beginning of an even more daunting challenge. Biden, who enters the White House as both the chief executive with the most experience in public service in US history and the oldest man to assume the presidency, will take on his duties amid a historic crisis, a pandemic that has already claimed more American lives than World War I, the Korean War, and the Vietnam War combined and has produced the highest unemployment rates since the Great Depression.

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And Biden and Harris may have to take power with a Republican Senate. As of this writing, the small chance of a Democratic Senate hinges on runoff elections in Georgia in January and uncalled races in North Carolina and Alaska. A slight majority for Republicans is very likely. A Democratic failure to take the upper house — even if they hang on to the House of Representatives as expected — could effectively end Biden’s agenda before it has a chance to take form.

Biden won the presidency by partially rebuilding the so-called “blue wall” for Democrats — the industrial Midwestern states of Michigan, Wisconsin, and Pennsylvania. He also planted a Democratic flag in the Sunbelt, with Arizona, Georgia, and North Carolina all still in play (Biden leads in the first two and is behind in the third). As of this writing, he has amassed 73.7 million votes to Trump’s 69.6 million — a spread of 50.5 percent to 47.7 percent — and can lay claim to the record for most votes in US history.

As the scale of the pandemic and its economic damage started becoming clear earlier this year, the Biden campaign signaled that the candidate wanted an “FDR-sized” administration. He touted a plan to tackle the Covid-19 pandemic by expanding testing, fostering better coordination between states, and organizing rapid development and deployment of a vaccine. He put forward a program to fight the economic crisis created by Covid-19, including funding for states and localities, cash and unemployment insurance for individuals and households, and grants and loans to small businesses like bars and restaurants.

All that seems fairly doable under unified Democratic control — but much, much harder if Sen. Mitch McConnell keeps the Senate. In 2009, McConnell decided that a posture of absolute obstruction, meant to block any and all Obama legislation meant to rescue or reform the economy, was the best approach for Senate Republicans. At that time, his Republicans were in the minority, so total obstruction was harder. This time, he may have a Senate majority — and he is likely to take that posture again.

Without the Senate, Biden’s ability to enact his agenda will be severely constrained, even if there are executive actions he can take to move the ball on a few fronts. He will have a little more latitude in foreign affairs, where he’ll seek to undo Trump’s reversal of the Obama-Biden foreign policy by re-engaging with Cuba and Iran, negotiating a new arms control deal with Russia, and addressing the threat North Korea poses to South Korea and Japan.

Biden will also have to decide how to handle the legacy of his predecessor: whether to let bygones be bygones, as was the Obama-Biden attitude toward George W. Bush, or to seek to prosecute, or at least investigate wrongdoing from the Trump years under a new attorney general.

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All these questions will have to wait until we know the outcome in the Senate. For now, at least, Democrats can celebrate winning the presidency.

Trump’s defeat comes as an enormous relief to the majority who voted against Trump four years ago, to those harmed by his policies from forced family separation to the botched Covid-19 response, and to the many who worried Trump harbored dangerous autocratic tendencies. To the Americans who elected Biden, it feels like the ending of a dark chapter in our nation’s history, and potentially the beginning of a moment of great opportunity.

But for that opportunity to be fulfilled, Biden and Harris will need to work fast — and we won’t know if they’ll be able to do that until we know the results in the Senate.

The Biden-Harris agenda

At stake is an agenda that rivals any previous Democratic president’s program.

Biden’s plan to respond to the Covid-19 disaster is called “Build Back Better.” It doesn’t have quite the same ring as “New Deal” or “Great Society,” but it captures what Biden is aiming to do: rebuild from the wreckage left by the Trump administration’s failure to contain the virus and willingness to let it spread to 9 million cases and over 230,000 deaths.

That failure has led to the highest unemployment since the Great Depression (14.7 percent in April; and 7.9 percent in September) and surging poverty. Meanwhile, as the pandemic raged, the Trump administration responded to protests for racial equality in about the worst and most divisive way imaginable.

That’s the baseline, and the Biden-Harris team has committed to massive spending programs, both on Covid-19 and other challenges from climate to caregiving, to rebuild from it.

To tackle Covid-19, Biden has promised nationwide testing, a 100,000-person Public Health Jobs Corps, hazard pay for essential workers, massive vaccine stockpiles produced ahead of approval for the speediest deployment, and much more.

On the economy, Biden is proposing a bevy of plans that collectively amount to the most ambitious agenda for a Democratic candidate in decades. The plans are oriented in particular around rebuilding (green) manufacturing in the US, building on the safety net expansions made by Obama, and dramatically expanding access to child, disabled, and elder care services.

His economic recovery plan to address the Covid-19 downturn would pay health insurance costs for newly unemployed people, offer middle-class parents and caretakers $8,000 a year for child or long-term care support, spend $700 billion on manufacturing and R&D to expand jobs in those sectors, and make it easier to organize unions.

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His climate plan features $2 trillion in investments in clean energy and a clean electricity standard mandating that electricity production in the US not produce any carbon by the year 2035.

But even if Democrats end up taking the Senate, the path ahead for the Biden-Harris agenda remains tricky. A GOP in the Senate minority led by Mitch McConnell would likely repeat McConnell’s 2009-2011 strategy of attempting to block every one of the new Democratic administration’s initiatives. That strategy meant the Obama-Biden administration and its allies in Congress were forced to compromise on elements of financial reform, abandon a public option for health care, and dramatically shrink a major stimulus package, prolonging the Great Recession as a consequence.

To prevent repeating that fate, Biden and a hypothetical Democratic Senate majority would have to abolish the filibuster, as former President Obama and former Senate Majority Leader Harry Reid have strongly urged. Senate Democratic leader Chuck Schumer has been very clear that abolishing the filibuster is “on the table” in the new Congress.

Biden will also have to deal with a hostile Supreme Court, especially now that Amy Coney Barrett has been confirmed to replace Ruth Bader Ginsburg.

Things look even worse for Biden if Republicans keep the Senate. Much of his agenda is likely to be dead on arrival. In that case, Biden will have to decide how to use what little leverage he has, like the ability to force a government shutdown, to pressure McConnell, and he will have to decide which issues he will use that pressure to push.

Biden will also lean on his reputation as a moderate, bipartisan dealmaker to get things out of Congress. When I spoke to Biden economic adviser Benjamin Harris, he explained that Biden plans to leverage his relationships in the Senate to pass his agenda with bipartisan support.

“I’ve spent a lot of time in the vice president’s office when he was vice president. I sat there when he called Democratic members, and I sat there when he called Republican members,” Harris recalled. “That’s what happens when you spend so many decades in the Senate is you build these friendships and you build these relationships and you build this credibility.”

In that scenario, McConnell will also have to decide just how obstructionist his Senate GOP caucus can be without incurring public blame for inaction. Given the narrow margin, and the fact that 21 Republican seats and only 13 Democratic ones are up for election in 2022, Senate Republicans will also need to put together a defensible record of governance if they hold the body.

Bringing the curtain down on the Trump presidency

Joe Biden has won the presidency, but it’s far from clear if he will be able to form a government, in the sense of commanding enough legislative votes to regularly pass budgets and other essential legislation. He will likely also face Senate obstruction with his picks for key Cabinet positions necessary to run the government effectively.

This is an unusual situation in most rich countries, which typically use a parliamentary system where a failure to assemble a governing coalition triggers new elections. In America, however, over the past 30 years, the same party has controlled the House, Senate, and presidency only one-third of the time. This dysfunctional system gets defended as Americans wisely preferring divided government (only a small minority of Americans actually do).

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But our system has tremendous costs. It brought the US to the brink of default in 2011, because neither Obama nor House Republicans had the capacity to simply enact their agendas. While the parties were able, remarkably, to come together and pass a massive stimulus in March, they’ve failed to renew it since August, at immense human cost. Both parties have plans, but a divided government has meant none of them get passed. If Biden and McConnell are forced to negotiate the next stimulus package, a similar stalemate might ensue.

But that’s all still ahead of us. For now, Americans can mark the end of a vicious and interminable campaign — and a presidency that a majority of the country has rejected.

The last four years have been consequential for the lives of Americans, from policy changes in the normal range of Republican presidencies (like Trump moving the Supreme Court markedly rightward and curtailing environmental and public safety regulations) to ones well outside it (like Trump’s enormous crackdown on legal immigration and his failed pandemic response).

The public has also endured truly unprecedented levels of executive branch corruption and arguably criminality, not to mention a historic presidential impeachment.

Biden’s victory is America’s first step away from those changes and the crew who made them. But it’s only a first step. It won’t instantly clean up the wreckage of the Trump administration, let alone the problems that enabled Trump to win and thrive in the first place. And the scale of his achievement will depend entirely on the Senate outcome in a handful of states.

Biden and Harris supporters are entitled to celebrate. Americans traumatized by the Trump presidency can breathe a sigh of relief. Then it’s time for them, and the new president, to get to work.