WASHINGTON • Missouri's vote Tuesday against a core feature of the nation's new health care law further emboldened GOP critics while reminding Democrats of the perils of pursuing change that doesn't enjoy broad public support.

With the requirement to buy health insurance not taking effect until 2014, the wrangling in the judiciary has years to play out. But the politics surrounding the insurance law accelerated swiftly after the vote.

Republicans trumpeted Missouri's passage of a ballot proposition aiming to nullify the provision of the new health care law requiring that all Americans purchase insurance. GOP leaders in Washington pointed to the Proposition C's passage with 71 percent of the vote as a further repudiation of the new health insurance law and a signal of their impending good fortunes in November.

The measure won a majority of voters in every county in the state except for Kansas City and St. Louis city, according to the Missouri secretary of state's office.

Supporters of the sweeping new health care law sought to minimize the impact, noting that the proposal was destined to pass overwhelmingly given popular GOP primary contests in Missouri and the heavy Republican turnout.

White House spokesman Robert Gibbs called Proposition C a "vote of no legal significance in the midst of heavy Republican primaries."

Sen. John Cornyn, R-Tex., chairman of the National Republican Senatorial Committee, criticized Gibbs' assertion that the Missouri vote told him "nothing."

"This sheer arrogance and political tone deafness from the Obama White House is simply astounding. Their disregard for the votes that were cast by 667,000 Missourians as 'nothing' is startling ..." Cornyn said in a statement.

The ballot measure now awaits an expected court test, along with challenges by elements in 20 states of various parts of the new law. At least two other states — Arizona and Oklahoma — have measures similar to Missouri's on their November ballots.

Some legal scholars contend that state efforts such as Proposition C stand little chance of success because the Constitution gives Congress the power to regulate commerce.

Nonetheless, a lawsuit brought by Virginia's Republican attorney general challenging the insurance mandate survived an initial court test on Monday when a federal judge rejected arguments by the administration of President Barack Obama that Virginia had no standing to challenge the law.

Richard Reuben, a law professor at the University of Missouri-Columbia, said he would anticipate a challenge to Proposition C originating in Missouri. Reuben said he saw a conflict between Missouri's ballot initiative and the Constitution.

He added: "But when it gets to the courts, which it will, there's a question of how they will react. Liberal courts will treat it one way and conservative courts will treat it another way. So when it gets up to the Supreme Court, if it makes it that far, I think all bets are off."

Rob Jesmer, executive director of the National Republican Senatorial Committee, distributed a memo Tuesday referring to Missouri and contending that "there's no doubt that his (Obama's) health care bill will be among the key issues voters weigh this November."

GOP candidates from Washington to Jefferson City seized on the Proposition C vote as an affirmation of their protracted campaign against the new insurance law and a signal that their anti-big government theme pays dividends.

Campaigning in Jefferson City, Rep. Roy Blunt, who won Missouri's GOP nomination for the Senate on Tuesday, asked: "Can you imagine a louder voice at the ballot box than Missourians shouted out yesterday when they said, 'No, we don't want to be part of this government-controlled health care bill'?"

Missouri Sen. Claire McCaskill's reaction to the vote illustrated the muted response by Democrats.

"Sen. McCaskill understands the distrust that Missourians have of their government. She is going to keep working to inform Missourians of the benefits of the law, and she will work to make changes if they don't work," a spokeswoman for McCaskill said.

Senate Majority Leader Harry Reid, D-Nev., noted Missouri's modest turnout, which was 23 percent. "It's very obvious that people have a lack of understanding of our health care reform bill," he said.

Health care advocacy groups characterized Missouri's sentiments on Proposition C as "political theater" rather than an expression by voters destined to have impact. They said they hoped it didn't distract the state from applying for grants, setting up a new insurance exchange and otherwise preparing for the law's staggered provisions to take effect.

Kathleen Stoll, director of health policy at Families USA, a Washington-based advocacy group, said that the outcome of Proposition C was determined "predominately by voters who were interested in weighing in on the Republican primary. I don't think that this is a true reflection of the public's understanding of what's in the new law."

Polls have showed the new health care law remains unpopular with many Americans, sometimes most. But of all its provisions, voters remain most suspicious of the requirement that they buy insurance or pay a fine.

When the Kaiser Family Foundation conducted one of its periodic polls this summer, 65 percent viewed the individual mandate unfavorably — the most negative response of a series of questions asked about the new law.

Molly Ann Brodie, Kaiser's director of public opinion and research, said of the Missouri vote: "It's important to recognize that there's a lot of division and dissatisfaction in the country right now and that people who are against what is going on in Washington are going to be against the health care law."

Brad Coker, managing director of Mason-Dixon Polling & Research, said that the Proposition C vote reflected the unpopularity of Obama and White House policies in Missouri that showed up in his poll last month for the Post-Dispatch.

He observed that Democrats were having a difficult time defending the insurance law, much as Obama had a hard time selling it.

"It's kind of hard to champion something that remains very mysterious to people," he said.

Virginia Young of the Post-Dispatch contributed to this report.