Even as Rick Santorum steps up his attacks on Mitt Romney over health care, Senate Republicans are expressing confidence in the GOP presidential frontrunner and his ability to lead their party on this crucial issue come November.

Santorum, speaking Monday on the Supreme Court steps, said Romney is disqualified to lead the Republican ticket this fall because his Massachusetts health care law was the forerunner to President Barack Obama’s reform law. But Republican Senators, citing federalism and Romney’s promise to repeal “Obamacare,” insist that the former Bay State governor would be a strong voice for the GOP in the general election — even in a campaign that hinges in part on the controversy over the health care law.

“I still don’t like the plan the way it ended up in Massachusetts, but I like the fact that he tried to solve a problem,” Sen. Jim DeMint (R-S.C.) said in an interview last week after meeting with Romney on Capitol Hill. “It’s very different than a federal model that you can’t change — that doesn’t give any states the right to do something different.”

“The laws are different,” Sen. Marco Rubio (R-Fla.) added. “The issue here is not some state’s law. The issue here is whether the federal government should have a 50-state solution for our health insurance problems. And the answer is that at least the solution the Obama administration came up with is not the right one.”

The Supreme Court is in the midst of oral arguments to determine the constitutionality of the Affordable Care Act, Obama’s 2-year-old health care reform law. Santorum is hoping to use the renewed national focus on the legislation to blunt Romney’s apparently inexorable march toward the 2012 GOP presidential nomination. Conservatives deride the law, which is credited with the rise of the tea party and the GOP’s overwhelming success in the 2010 midterms.

Santorum has argued that the similarities of the president’s federal law and Romney’s state law — both of which include a mandate to purchase health insurance — render the frontrunner a weak candidate, particularly if the economy recovers and unemployment recedes.  Santorum has dismissed Romney’s vow to repeal the law as a position voters wouldn’t take seriously.

In fact, White House adviser David Plouffe said during interviews Sunday that Romney is the “godfather” of Obama’s health care law.

“He’s the worst candidate to go against Barack Obama on the most important issue of the day,” Santorum said at his news conference Monday. “We need someone in this race who can actually make a contrast.”

A year ago many political observers said the Massachusetts law would be an albatross for Romney, but as the former governor has continued to steadily win convention delegates, he has also begun to accrue the support of stalwart conservatives. On Monday, House Majority Whip Kevin McCarthy (R-Calif.) endorsed Romney, as did Sen. Mike Lee (Utah), a tea party Republican elected in 2010 after ousting Bob Bennett in a primary convention.

American Conservative Union Chairman Al Cardenas also endorsed Romney on Monday.

Meanwhile, conservatives who haven’t officially backed Romney, such as DeMint, Rubio and Sens. Ron Johnson (R-Wis.) and Pat Toomey (R-Pa.), are speaking favorably of the former governor’s conservative credentials and his ability to lead the party against Obama in an election that they hope will at least partly revolve around the need to reduce spending, debt, and the size and scope of government.

This might also reflect that Republicans have tired of a primary contest that many view as damaging the GOP and boosting Obama politically. But Romney’s supporters, while acknowledging his occasional campaign missteps, contend that the governor is the Republican candidate best-positioned to challenge the president, particularly on the economy. On health care, they dismiss any suggestion that he is compromised on the issue.

“I totally disagree,” said Sen. Rob Portman, who endorsed Romney in January. The Ohio Republican said Obama and the governor “couldn’t be further apart” on health care.

“He believes in repeal, and he has an alternative that will work better,” Portman said of Romney. “That will be the contrast. I’ve never understood this argument that somehow there won’t be a sharp difference of opinion between the two. There’s a very sharp difference of opinion. President Obama can say whatever he wants about Massachusetts. The fact is, this election’s about the country, and they have two competing visions as to health care.”

“I think he has made [repeal] one of the key elements of his campaign,” added Sen. John McCain (R-Ariz.), another Romney backer.