WASHINGTON (CNN) -- The main event during Tuesday night's Republican presidential debate in Michigan is Fred Thompson's debate debut.
Fred Thompson, joined by his wife, Jeri, prepares to address the "Defending the American Dream" summit.
The former Republican senator and "Law & Order" star's plan is to assert himself as the "common sense, consistent conservative" and harken back, as he does on the campaign trail, to his place in the Class of 1994 that led the Republicans to their historic capture of the House and the Senate.
Look for rivals, though, to question the credibility of Thompson's effort to place himself in the shadow of Ronald Reagan during the debate, which is sponsored by CNBC, the Wall Street Journal, the Michigan Republican Party, and the University of Michigan-Dearborn.
Already, rivals have suggested he was more of a centrist in the Senate -- in their view someone who put concerns about balancing the budget ahead of any zeal for trusting tax cuts to eventually lead to more government revenues.
And several vague statements Thompson made as he explored the race could come into play.
Thompson, for example, has said he believes all options should be considered when the government looks at major problems. He is on record as saying he believes it would be wrong to absolutely rule out a gas tax increase as part of any major energy package, or a tax increase of some sort as part of major reforms designed to shore up Social Security.
Thompson aides say such answers simply meant that no president can expect good-faith negotiations if he or she rules things out before any conversations with others, but Thompson rivals suggest they show a candidate open to raising taxes.
A senior Thompson aide involved in the debate preparations played down the "first debate" buzz and said Thompson "needs to be himself."
The aide also suggested Thompson doesn't need to go on the attack but said, "if there is one goal," it was for Thompson to show he was the best conservative to beat the Democratic candidate in a the general election, particularly the Democratic front-runner, Sen. Hillary Clinton of New York.
While all eyes will be on Thompson, another story may be the extent to which front-runners Rudy Giuliani and Mitt Romney go after each other.
Romney has for days been attacking Giuliani's record during his tenure as the mayor of New York, suggesting the national GOP front-runner is anything but a fiscal conservative.
In an e-mail sent Monday titled "Big City, Big Spender," the Romney camp charged the New York City budget grew more than 37 percent during Giuliani's time in office and that Mayor Michael Bloomberg, Giuliani's successor, was left with a projected budget gap of $1.3 billion.
The Giuliani camp was silent for several days but now is returning fire -- noting fee increases and spending increases during Romney's tenure as Massachusetts governor.
The Giuliani campaign also fired off its own fact sheet, saying Massachusetts economic growth lagged behind the national average during Romney's tenure and the Massachusetts state budget grew 22 percent during Romney's time in office.
Friday morning, Steve Forbes, national co-chair of Giuliani's campaign, also defended Giuliani.
"Results speak louder than rhetoric," Forbes said in a statement. "That's why Rudy Giuliani's record of cutting taxes and slashing government spending makes him the true fiscal conservative in the race."
With Romney considered the "state by state" front-runner because of his leads in Iowa and New Hampshire, the increasingly brittle tone between these two camps is viewed by many as proof what has been a relatively civil GOP contest so far is about to turn more testy, if not nasty.
The Michigan debate may also be a test for Sen. John McCain and his re-energized campaign. The Arizona Republican is alone among the GOP contenders in routinely talking about global warming and climate change as a major challenge for the next president.
McCain won Michigan in 2000 and is within striking distance this time, but he could face questioning about what his views on the issue would mean for the struggling U.S. auto industry, which is based in Michigan. E-mail to a friend
CNN's John King and Scott Anderson contributed to this report.