Another mistake. Like the New Hampshire Union Leader said earlier this week:

If Thompson waits until after the debate to make his announcement, it will appear to some as if he timed the announcement just to avoid the New Hampshire debate. That would give his foes the chance to say he is either not serious about running for the nomination or is too unprepared to be considered a credible candidate…

Thompson’s main weakness right now is his commitment to the race. Republicans are starting to think that his heart is not in it, and they are getting tired of the teasing. The best way for Thompson to dismiss this concern and prove he is a serious and credible candidate is to take up the challenge and join his rivals on stage on Sept. 5.

Running an ad during the actual debate only reinforces the impression that he wants the audience but isn’t willing to face the other candidates to get it. It’s also tremendously hubristic insofar as it’s transparently an attempt to upstage the rest of the field. Raising expectations further is the last thing he wants to be doing right now. Quoth the Times: “Republicans close to the Thompson campaign felt that the risks [of participating in the debate] would probably be too great for any benefit. In the worst case, he might have made a mistake or come under attack from his Republican rivals, overshadowing the highly scripted rollout he has prepared for the next day.”

Stephen Hayes, who is to the Thompson campaign what Hewitt and my pal Barnett are to Team Romney, lays out the plan:

On Wednesday, September 5, shortly after his Republican rivals debate in New Hampshire, he will appear on The Tonight Show with Jay Leno to announce that he will be launching his campaign the following day in a speech broadcast on his website, imwithfred.com. That evening, he will call in to supporters gathered at Thompson-for-president house parties across the country. Thompson will travel immediately to Iowa, New Hampshire, and South Carolina–three critical early primary states. The second leg of the launch tour will include several stops in Florida, which Thompson strategists have long viewed as critical to their bid to win the Republican nomination. He will finish his initial campaign foray with a visit to his hometown of Lawrenceburg, Tenn., on Saturday, September 15…

All of this means one thing: Thompson wants to position himself as the only viable conservative alternative to Rudy Giuliani. In conversations with several Thompson strategists over the past week, one phrase was repeated nearly a dozen times: consistent conservative. It is a not-so-subtle reminder, they say, that Giuliani is not a conservative and that, while Mitt Romney may sound like a conservative now, he has not been consistent.

Take out Mitt and then hope the social con base carries you through. The problem is that Mitt is way ahead in Iowa and New Hampshire, to the point where he’s already a virtual lock to win there. That makes South Carolina a must-have for Fred, where he’s ahead in one poll and will need the win to prove the south is on his side before the showdown with Rudy in Florida on January 29. Expect Mitt to start spending serious money in SC sometime soon to try to steal the state and prove that Fred’s a paper tiger who can’t even win on his (virtual) home turf.

Update: Here’s why he looks thinner lately. Money quotes:

Ari Fleischer, former press secretary to President George W Bush, said: “From the moment that Thompson declares, he has about a one-week window for people to say he’s for real or not. If people get a let-down feeling after his announcement, because he got in so late, it will be harder for him to recover.”…

Thompson will be seeking to detach voters from Mitt Romney, the former governor of Massachusetts and a Mormon, who has a slick, well financed campaign and is beginning to win over evangelical Christian voters. “If we had Romney’s organisation and Fred’s personality, the race would be over,” said a Thompson insider.