MANCHESTER/NORTHFIELD, New Hampshire (Reuters) - Republican presidential upstart Rick Santorum found himself under increasing scrutiny on Thursday as front-runner Mitt Romney tried to chip away at his credibility ahead of the key New Hampshire primary.
Santorum's surge in Iowa, which held its nominating contest on Tuesday, was so quick that his record as a U.S. senator and strong conservative views against abortion and gay marriage escaped close attention from his 2012 presidential rivals and the media.
A Suffolk University tracking poll showed Romney on cruise control in New Hampshire ahead of its primary next Tuesday but that Santorum had risen to a distant third. It gave Romney 41 percent support, Ron Paul 18 percent and Santorum 8 percent.
After finishing a close second to Romney in Iowa and bursting into the limelight, Santorum is under the microscope, drawing fire from Senator John McCain, a Romney supporter who clashed often with Santorum over government spending when they were Senate colleagues.
McCain, the 2008 Republican presidential nominee, is a sharp critic of spending items called earmarks that typically escape the scrutiny that accompanies U.S. budget legislation, to the dismay of conservatives.
"He was an avid earmarker and a staunch defender of porkbarrel spending," McCain told Reuters. "I just don't think he can portray himself as a fiscal conservative. We all know that earmarking is a 'gateway drug' to corruption."
Santorum's efforts to obtain taxpayer funds for spending projects for his home state of Pennsylvania have long been an issue. McCain specifically cited the $500,000 that Santorum engineered for a polar bear exhibit at the Pittsburgh zoo as an example of wasteful spending.
"The polar bears are living well," McCain said wryly. "That's the good news."
Santorum has fought back against accusations of profligate spending, saying he wanted to make sure his taxpayers got their "fair share" of money back. He says he will fight for deep spending cuts if elected next November.
Santorum is hoping to recreate his Iowa magic in New Hampshire, which holds the second contest to determine a Republican challenger to Democratic President Barack Obama.
He wants to finish strong enough to generate momentum going into South Carolina, where a conservative like him has a better chance.
"Obviously Mitt Romney is at 40 percent in the polls, the chances in five days to make up a 35 or 40 point lead is going to be pretty limited but we expect to make a run and to move up in those polls," Santorum told reporters in Manchester.
Romney's big lead gives him great expectations in New Hampshire, perhaps more than he can reasonably expect to fulfill in a state that is unpredictable and can provide crucial momentum to the second-place finisher.
McCain said he believed the race will tighten in New Hampshire and doubted Romney will end up with 40 percent support or more.
"It's important for the Romney campaign and all of us who are supporting him not to raise expectations," said McCain, who surprised George W. Bush here in 2000. "So much of this is the expectations game. I think he'll win New Hampshire well but I can't imagine any candidate winning with 43 percent of the vote."
Keeping Obama in their sights, the Republicans blasted Obama for bypassing Congress to fill politically sensitive posts.
Obama upset Republicans by making four recess appointments - naming Richard Cordray to run the new Consumer Financial Protection Board and filling three vacancies on the National Labor Relations Board.
Ron Paul called Obama's move a clear disregard of the U.S. Constitution.
"The president must be called to account for his actions," Paul said in a statement, adding that Congress may need to take action to rein in Obama's "flagrant contempt" for the rules.
The top finishers in New Hampshire will carry important momentum toward what will be a showdown on January 21 in South Carolina, where a conservative has a better chance.
So far, Romney has not gone after Santorum with the same intensity as he did against former House of Representatives Speaker Newt Gingrich, who led the polls in Iowa before being attacked in millions of dollars of negative attack ads.
That experience has left Gingrich an angry revenge-seeker. He is campaigning in New Hampshire accusing Romney of being a "timid Massachusetts moderate" who lacks conservative principles.
Gingrich is hoping to finish high enough in New Hampshire to give him momentum going into South Carolina, which this year may hold the key to the Republican presidential nomination. A second objective is to prevent Romney from having a blow-out victory.
"I don't believe that a Massachusetts moderate is in a very good position to debate Barack Obama," Gingrich said.
Additional reporting by Ros Krasny and Scott Malone; Editing by Eric Walsh