Mitt Romney, fighting his way back into the driver's seat in the Republican presidential race, assailed rival Rick Santorum on Thursday as a Washington insider in a line of attack that polls show seems to be working.
After repeatedly putting the former Pennsylvania senator on the defensive in a debate on Wednesday over Santorum's record of backing big spending in Congress, Romney kept up his attacks at a campaign appearance in Arizona.
"I don't know that I've ever seen a politician explain in so many ways why it was he voted against his principles," Romney told a builders' conference in Phoenix.
Romney lampooned Santorum's comments during Wednesday's debate that he sometimes had to vote for bills he did not like - including spending programmes, education reforms and increases in the federal debt - because politics was a "team sport."
"He talked about this as taking one for the team," said Romney, a former Massachusetts governor and venture capitalist. "I wonder which team he was taking it for? My team is the American people, not the insiders in Washington."
Arizona and Michigan are the next battlegrounds in the state-by-state battle to pick a challenger to President Barack Obama in the November 6 general election, with crucial nominating contests next Tuesday.
While Santorum, a social conservative, has courted controversy with comments about abortion and gay marriage and the role of women in the military, Romney seems to have struck a chord with his portrayal of Santorum as a supporter of big spending.
Romney is fighting to regain the top spot in the Republican presidential race, and holds a slight lead in a poll in Michigan after trailing Santorum by as much as double digits a week ago there.
Any comeback by Romney would be well-timed, with 10 Super Tuesday primaries coming on March 6.
On Thursday, Romney won a restrained endorsement from Michigan's largest newspaper, the Detroit Free Press - with the caveat that he stop "chest-beating" to prove his conservatism and return the focus to his record and collaborative leadership.
The primary in Michigan, where Romney was born and raised and his father was an auto executive and popular governor, has become critical for him.
A loss there would set off alarm bells about Romney's ability to win the allegiance of conservatives and ensure a long and costly battle to find a challenger for Obama in the general election.
But a win there and in Arizona would put Romney back in command in a race that has featured a series of conservative rivals who have risen to challenge him only to fall back into the pack.
Polls in Michigan and Arizona on Wednesday showed Romney gaining ground. He held a slight 2-point edge on Santorum in an NBC/Marist poll in Michigan, and a 16-point edge in an NBC/Marist poll in Arizona, where a CNN/Time poll earlier in the week gave him just a 4-point edge.
Romney's well-financed campaign has turned it sights on Santorum in TV ads, in a repeat of a barrage of attacks it launched against Newt Gingrich, a former speaker of the US House of Representatives, who surged then fell.
The Romney campaign, which as of last week had spent about $1 million on two weeks' worth of advertising in Michigan, is running an ad that shows a man in a suit with a briefcase drowning as the narrator talks about America drowning in debt while Santorum supported big-spending projects.
Santorum also is under fire from another Republican hopeful, US Representative Ron Paul, who called him a "fake" fiscal conservative in a new Michigan ad and at the Arizona debate.
Santorum's campaign fired back at Romney with a new ad that reminds conservatives of some of Romney's shifting positions, including his former support for abortion rights and his backing of a Massachusetts healthcare law that became a precursor for Obama's federal overhaul.
"Since Mitt Romney refuses to talk about his own liberal record - we figured we'd show people what Mitt Romney says about Mitt Romney," Santorum spokesman Hogan Gidley said.
The debate was Santorum's first time in the political spotlight since charging into a national lead after winning three contests on Feb. 7 in Missouri, Minnesota and Colorado.
The pace of the Republican race quickens dramatically next month, with 22 states holding nominating contests in March, including 10 on "Super Tuesday" March 6.
The broader campaign battleground in March could allow Romney to exercise his financial and organizational edge on his rivals, and put him in a strong position to knock them out and wrap up the race at least by April, if not earlier.
In its endorsement, the Detroit Free Press criticized Romney for shifting away from his past stances and said he was "dead wrong" for opposing the government bailout for the auto industry.
But, the newspaper's editorial board wrote, "Romney, unlike the zealous Rick Santorum, the impulsive Newt Gingrich and the backward-thinking Ron Paul, is preferable to the rest of the field. He is the only one who has the combination of résumé and bearing to occupy the Oval Office."
Santorum may have missed his chance to change the campaign dynamic at Wednesday's debate.
"Santorum needed a strong performance in the debate and he didn't get it," Republican strategist Ford O'Connell said. "All eyes were on him. He had an opening and he missed it."
