JEFFERSON CITY • Republicans are for it.

Democrats are against it.

So what are Proposition C's chances on Aug. 3?

The ballot issue that asks voters if Missourians should be able to opt out of the health insurance mandate in the new federal health care law is likely to pass, according to a Post-Dispatch/KMOV-TV (Channel 4) poll.

The poll asked 300 likely Democratic primary voters and 300 likely Republican primary voters whether they intended to support Proposition C. Conducted from July 19-21, the poll question on Proposition C has a margin of error of 6 percentage points.

Republicans overwhelmingly said yes to the proposition, 67 percent to 16 percent, with 17 percent undecided. Democrats said no, 48 percent to 27 percent, with 25 percent undecided.

The heavy Republican opposition, combined with an expected heavy GOP turnout Aug. 3, leads to the likelihood that Proposition C will pass easily, said pollster Brad Coker, managing director of Mason-Dixon Polling & Research.

Even if the proposal passes, legal experts say the question of whether Missourians could really opt out of the federal health insurance mandate will be settled in court.

Supporters of Proposition C have pitched it as a referendum on President Barack Obama.

And in that regard, poll respondents were clear: They are unhappy with the president.

Statewide, 61 percent of those who responded to the Mason-Dixon poll said they opposed the health care law passed by Congress in March. Republicans opposed the bill overwhelmingly, with 91 percent saying they were against it. Among independents — the key demographic in a race in Missouri — 65 percent opposed the health care law.

Republicans in Missouri are expected to outnumber Democrats in the Aug. 3 primary because of high interest in the state auditor's race, as well as a contested primary in the GOP-heavy 7th Congressional District.

Mary Ellen Vose, a housewife from Atlanta, Mo., said she would support Proposition C.

"I don't think that the government should be forcing citizens to buy something they can't afford," Vose, 44, said. "Missouri should take a stand with the other states that are trying to do the same thing."

Of those who were polled, 92 percent said they had health insurance.

Missouri is the first of four states to plan "opt-out" votes.

Vose cited confusion with the new health care law in her reasons for opposing it.

"There was too much to it," Vose said. "Most of them who voted for it didn't even read the entire bill."

Health care is still an important topic to voters, though it has dropped in importance compared to the economy and jobs, which finished first in the poll among topics voters cared about.

"As an issue, we've seen it slide," Coker said of health care, which was one of the hottest topics among voters earlier in the year. "But it fits into the larger 'change' narrative."

One respondent, Johnnie Johnson of Berkeley, said it was reasonable to require all Americans to purchase health insurance.

It's not that much different than other insurance requirements, said the retired letter carrier and veteran.

"I think you should punish those people in certain categories if they don't fall in line. It's like when the policeman stops me and says, 'I want to see your insurance policy,'" Johnson, 65, said.

"I have to come up with some insurance document or I'll get a ticket."

Jake Wagman of the Post-Dispatch contributed to this report.