The former Tennessee senator, who had several months to prepare for a White House bid, entered the race 10 days ago and the early reviews have been less than glowing. Some Republicans have panned his performance as he's stumbled over a few questions right out of the gate.

"It's one thing to give a stump speech and project your theme, and he accomplished that with a conservative populist message," said Greg Mueller, a former aide to conservative Republican presidential hopeful Pat Buchanan in 1992. "Now, his next challenge is to really hone his answers to questions - and that's a challenge all candidates have faced."

In the unscripted moments, Thompson has faltered in the last week with several unforced errors.

Among them, he has:

-Referred to Osama bin Laden as "more symbolism than anything else" and was dismissive about whether it mattered if he were caught. Thompson made the remarks following the release of a new video from the terrorist leader and five days before the sixth anniversary of the Sept. 11, 2001, attacks. Democrats pounced, and Thompson then took a harder line, saying bin Laden "ought to be caught and killed."

-Declined to "pass judgment" on the appropriateness of Congress' intervention to save the life of brain-damaged Terri Schiavo two years ago. "That's going back in history. I don't remember the details of it," he said of the case that bitterly divided the nation, still energizes conservatives and helped sink the presidential aspirations of his former Tennessee colleague Bill Frist. Thompson did offer: "Local matters, generally speaking, should be left to the locals."

-Given an inartful answer on his personal religious practices while campaigning in South Carolina, where Christian evangelicals dominate the GOP electorate. "I attend church when I'm in Tennessee. I'm in McLean (Va.), right now," he said, adding, "I don't attend regularly when I'm up there."

-Blamed Democratic rival Hillary Rodham Clinton on Friday for the publicity surrounding his remark suggesting Cuban immigrants are bringing suitcase bombs to the United States. Even though he made the remark in June, and had to clarify it on his Web site the next day, he told a station in Miami: "I think that was a Hillary Clinton news release that she put out or a statement that she made trying to capitalize on something when she knew better."

Republican strategists say there is less margin for error for Thompson because he entered the race some nine months after his opponents and just four months before Republicans cast their ballots. Rudy Giuliani, Mitt Romney, John McCain and others have had most of the year to work out kinks and become adept campaigners before the high-stakes fall push when the spotlight - and pressure - is more intense.

"There are benefits to a late entry; there are costs as well, and one of those costs is scrutiny as you're getting your sea legs," said Tucker Eskew, a former aide to President Bush. "The unknown is whether he's getting his sea legs or whether this pattern will continue."

Thompson still ranks high in national polls and also is competitive in early voting states, but the coming weeks will be a true test of whether he can sustain such a strong position.

The actor-politician began toying with a presidential run in March and took a preliminary step in June. He delayed his official entrance until the fall, seemingly to get ready for a full-on campaign. But he spent much of the summer addressing internal staff upheaval as he looked to build a stable campaign organization - perhaps, some Republicans say, to the detriment of adequately preparing for the give-and-take of the campaign trail.