MESA, Ariz. • Mitt Romney and Rick Santorum clashed over which of them would be the true conservative steward of taxpayers' money Wednesday night, grappling for advantage as their two-man grudge match heads toward critical votes in Arizona and Michigan on Tuesday.

In a nationally televised debate on CNN, each Republican presidential hopeful cast himself as someone who would cut spending and slash a federal government grown large and wasteful. Each also accused the other of a record of wasteful spending in the past.

"During your years in Congress, government doubled in size," Romney said to Santorum, a former senator from Pennsylvania.

"Government as a share of the economy went down," countered Santorum. "I never raised taxes. ... Gov. Romney raised $700 million in taxes and fees," he said of Romney's term as governor of Massachusetts.

Rep. Ron Paul of Texas jumped in as well, slamming Santorum for calling himself a fiscal conservative. "He's a fake," Paul said, citing Santorum's vote for the No Child Left Behind education act and now campaigning to repeal it.

It was the last debate — and last chance to shake up the race — before Tuesday's primaries in Arizona and Michigan and then in 10 states on March 6, Super Tuesday.

Romney is locked in a neck-and-neck contest with Santorum in Michigan, with Santorum supported by 33.8 percent of likely voters and Romney supported by 33 percent, according to an average of public polls compiled by realclearpolitics.com.

A loss in Michigan would be embarrassing at the least for Romney, whose late father was chairman of a Detroit-based auto company and was a popular Michigan governor in the 1960s.

Romney leads Santorum in Arizona by an average of 8 percentage points in polls.

Their fiscal records dominated the early going in the two-hour debate. Santorum argued that he has proposed a detailed plan to cut spending by $5 trillion over 5 years.

"It's not inflation-adjusted, it's not baseline-budgeting," he said. "We're actually going to shrink the actual size of the federal budget, and we're going to do so by dealing with the real problem," which he said was excessive spending on entitlements.

Romney criticized Santorum's record in Congress, saying he had voted to raise the debt ceiling five times without demanding spending cuts in return and watching as federal spending grew by 80 percent.

Santorum said that federal spending shrank during his time in Congress when measured as a share of the overall economy. He also said that he had a more conservative voting record on budget issues than 50 other Republican senators.

"I was the most fiscally conservative senator in the years I was there," Santorum said.

"That's a cop-out, ranking yourself against other members of Congress," said Paul.

For former House Speaker Newt Gingrich, the debate was a chance to get back into the game after losing every contest since South Carolina on Jan. 21 and fading from sight. He used the spotlight to push an energy agenda that he said would cut gas prices to $2.50 a gallon.

FACT CHECKING

ROMNEY: Santorum "voted to raise the debt ceiling five times without compensating cuts in spending."

AP's take: Maybe so, but increases in the debt ceiling were not politically charged in the past. In fact, President Ronald Reagan, an icon to most conservatives, supported increases in the debt limit 12 times.

SANTORUM: "Gov. Romney today suggested raising taxes on the top 1 percent."

AP's take: Romney's new proposal actually would lower tax rates across the board.

GINGRICH: "When I was speaker ... we balanced the budget for four consecutive years."

AP's take: Gingrich has made this misstatement many times before. He can only claim credit for contributing to two years of a balanced budget, at most.