When? That's the question everyone is asking about Fred Thompson and his entry into the Republican presidential race.

Rep. Zach Wamp, who's been boosting Thompson since the beginning, says "in the coming days."

But Kelly O'Donnell reports that "sources close to" Thompson have already ruled out July, saying the announcement could "slip into early September."

In the meantime, here's a list of brief arguments why Thompson should jump in "Now" versus why he should jump in "Later":

Now:
1. The tease factor: The media will play the game for a while, like any good courtship, but there is a limit. With the pro-choice stories, the Nixon stuff, and egregious attacks on his wife, Thompson can't allow the media (or rival campaigns) to define him before he has a chance to define himself. With Congress out, August is a rough time for the Washington press corps. Best not test their patience.

2. The McCain factor: Like him or not, it's not a good sign for the party when one of its top candidates falls so spectacularly. And while the anti-McCain Republicans are cheering right now, so are the Democrats, who see an opposition bitterly divided among itself. McCain's downfall in some ways illustrates that division. Thompson, on the other hand, has the ability in the eyes of GOP voters to bring the party back together. He has to earn it, but announcing shortly after the McCain mess would be an opportune time to raise GOP spirits.

3. Money: Marc Ambinder has the details of Thompson's money conundrum. The short version is that Thompson is doing everything the law allows so that he doesn't have to disclose his fundraising numbers, for various reasons. While there's nothing sinister about this, it never looks good when a candidate is seen as not being completely forthright with money matters.

Later:
1. The polls: If things keep going the way they're going for Fred, he could be the front-runner by September without having announced. Seriously, though, as long as Thompson stays on top of his fundraising and public appearances, there's little evidence to suggest that an announcement would do much to help him.

2. The Aug. 5 Des Moines, Iowa, Debate: As Jonathan Martin lays out, it's in Thompson's best interest now to miss this debate. Rudy Giuliani was off his game in the first GOP debate and it hurt him for weeks. Any bump Thompson might get in the polls from an announcement could be erased by a poor performance a week later. Besides, every commenter of every GOP debate so far has talked about the "Thompson Shadow" looming over the stage. The best part about a shadow is that it can't screw up a question.

3. The McCain factor: To watch a presumed frontrunner implode has been instructive for all the GOP candidates, but most of all for Thompson, who hopes to fill the spot left by McCain. The episode should leave two distinct impressions: 1.) have a message, preferably one that doesn't turn off half the GOP electorate; and 2.) have a team in place to project that message, preferably one that appreciates your weaknesses and accentuates your strengths. Easy to say, harder to achieve, which is why Thompson is taking his time to hone his message and build his organization.