WASHINGTON - If you thought passing the health care overhaul was messy, wait until Republicans try to repeal it if they regain power this fall.

It could come down to who blinks first, with some Republicans raising the prospect of a government shutdown.

Even if Republicans succeed beyond any current predictions and capture both the Senate and the House, they wouldn't have enough GOP votes to overcome President Barack Obama's veto.

But Republicans could still fall back on the congressional power of the purse, denying the administration billions of dollars to carry out the most far-reaching social legislation since Medicare and Medicaid.

"The endgame is a fight over funding," said Sen. Tom Coburn, R-Okla.

Faced with an opposition Congress "defunding" his health care plan, would Obama make a stand? Would he risk shutting down the Health and Human Services department, the IRS, or perhaps even the whole government?

"At that point, does he let everything else go?" asked former Rep. Tom Davis, a Virginia Republican elected in the GOP wave of 1994. "The game will be, does he shut the government down? Republicans can say, 'We gave him the money to fund other programs.'"

Davis, a moderate who watched former Speaker Newt Gingrich lose a confrontation with then-President Bill Clinton over a government shutdown, cautioned both sides: "The question is, do you win that argument or not?"

White House officials wouldn't comment.

The No. 2 House Democrat dismissed the talk of repeal as wishful thinking by Republicans. Majority Leader Steny Hoyer, D-Md., said he's confident Democrats will stay in charge.

Even if Republicans win, "they can beat their chests and say they won't fund the implementation of the law, but I think the law is the law, and if you can't change it, then, frankly, you have a responsibility to carry it out," Hoyer said.

But months after Obama signed the legislation, extensive efforts by his administration to tout its benefits for seniors and families, small employers and large corporations, have failed to rally public opinion.

Major components such as taxpayer-subsidized coverage for millions now uninsured, an IRS-enforced mandate that most Americans carry a policy, and guaranteed coverage for people in poor health are still more than three years away.

That's a tantalizing opportunity for Republicans, and repealing "Obamacare" has become a campaign slogan in their drive to take the House. Some have proposed replacing the law with more modest alternatives.