Review: Conan returns to late-night TV with ease

In this photo provided by TBS, Conan O'Brien performs during the debut of his new TBS show " Conan" on Monday, Nov. 8, 2010.

ROCHESTER, Mich. -- Republican presidential candidates will debate tonight for the first time since Herman Cain became controversial, Rick Perry unveiled his optional flat-tax plan and Mitt Romney explained in detail how he would reduce budget deficits.

Cain, who on Tuesday strongly denied accusations of aggressive sexual behavior by several women, will be watched most closely.

Can he, analysts are asking, regain the stature and popularity that put him at or near the top of most Republican presidential preference polls in recent weeks?

"People are still getting to know him, and the allegations are one of the most likely things people know about Herman Cain at the moment," said Matt Grossmann, an assistant professor of political science at Michigan State University.

Eight Republican candidates will spar for two hours, starting at 8 p.m. at Oakland University in Rochester, Mich., a Detroit suburb. CNBC will televise the debate.

They're supposed to talk about the economy in a state that has suffered more than most. Michigan's September unemployment rate was 11.1 percent, 2 percentage points above the national average.

"We've had what seems like a recession for 12 years," said Tom Shields, the president of Marketing Resource Group, a Michigan political-consulting firm.

Since the last GOP debate, on Oct. 18, Romney and Cain have remained at or near the top of national Republican preference polls.

Perry has been sinking, U.S. Rep. Ron Paul of Texas has maintained solid support around 10 percent, and former House Speaker Newt Gingrich has begun to climb to low double digits.

Cain, dogged by the sexual harassment accusations, is stumbling. An NBC/Wall Street Journal poll taken last Wednesday through Saturday found that 35 percent said they viewed Cain negatively -- double last month's number.

Gingrich has seen his standing in polls rise from below 5 percent to 10-12 percent in the past few weeks.

Perry has a different challenge -- demonstrating gravitas. He's dropped far from the top tier of national polls, and the Perry camp hoped that his tax plan would give him a boost among conservatives.

The proposal would give taxpayers the option of using the current tax system or paying 20 percent of their incomes after deducting $12,500 per person, state and local taxes and charitable contributions.