If George Allen is successful in his bid to take back the U.S. Senate seat from Virginia that he lost in 2006, he could serve as a litmus test for whether Republicans have learned anything since the Bush era.

Right now, conservatives are hoping that Mitt Romney defies the critics and beats President Obama, while Republicans hold on to the House of Representatives and gain control of the Senate.

But even if all of this happens, the big question is whether Romney and his fellow Republicans would follow through on his promises to rein in the size and scope of government. Though Republicans often talk a big game about cutting spending when Democrats are in power, they haven't delivered on their promises when they've been in control.

In the previous decade, President Bush, with the help of the Republican-controlled Congress, tossed aside limited-government principles, and spending soared from $1.86 trillion in 2001 to $2.98 trillion in 2008, according to the Congressional Budget Office. That's an increase of 60 percent. Not only did Bush fail to reform entitlements, he pushed the largest expansion of entitlements since Lyndon B. Johnson in the form of the Medicare prescription drug law.

Allen's first term in the U.S. Senate, from 2001 to 2007, covers the bulk of the Bush era. During that time, he took earmarks, voted for No Child Left Behind and for the Medicare prescription drug bill. In the time since he left the Senate, the emergence of the Tea Party has increased pressure on elected Republicans to get serious about reducing spending. Allen, who overcame a weak Tea Party primary challenge, is now navigating new waters.

In a meeting with the editorial board of The Washington Examiner this Tuesday, Allen argued for the urgent need to do something about the nation's mounting debt.

"I think now more then ever there needs to be constraints, there needs to be tough decisions made," Allen said. "I don't think our country's even got four or five years. We're lucky if we have two years to turn things around."

When he was running for re-election in 2006, Allen declared, "Every single earmark I've gotten, I'm proud of." But on Tuesday, he told The Examiner, "There should be no earmarks, I'm for the earmark ban." He even said Virginians shouldn't count on more federal funds to subsidize construction of the extension of Washington's Metrorail system to Dulles -- pork that his Democratic opponent, Tim Kaine, has promised.

Allen also conceded he had made a big mistake voting for Bush's No Child Left Behind law, which expanded the federal role in education and micromanaged states.

But when I asked Allen how believers in limited government could trust him to stand up to a President Romney on spending when he had failed to stand up to Bush on the Medicare prescription drug law, he was less apologetic.

"If you want to have a modern-medicine approach, not to have prescription drugs is really not taking into account the advancements in it," Allen said. He also said he backed the law because it advanced health savings accounts -- a common excuse for Republicans who backed it at the time, under heavy pressure from a Bush White House that wanted to run on the accomplishment in 2004.

When Medicare Part D was making its way through Congress in 2003, it was projected to cost $400 billion over a decade, none of it paid for by offsetting spending cuts. Over time, the benefit added $14.3 trillion to the nation's long-term entitlement deficit, according to the 2012 Medicare trustees' report.

With Republicans in the Senate divided between those sympathetic to the goals of the Tea Party and those more resistant to a sweeping reform agenda, Allen may help tilt the balance of the GOP caucus one way or another.

Philip Klein (pklein@washingtonexaminer.com) is a senior editorial writer for The Washington Examiner. Follow him on Twitter at @philipaklein.