Why the delay for Fred Thompson?

Politico.com has a few reasons.

Thompson’s team says it’s up to the former senator, and they really don’t know. The point, they say, is that he’s going to wait as long as possible without deflating the enthusiasm of his many vocal grass-roots supporters.

The advisers say that one factor in their calculation is the rapidly changing terrain of the race, and they point out that Thompson has already become a leading target for both Democrats and Republicans. Since he’s coming in first in some polls, including in Florida, and needs to overcome some complaints from former colleagues that he is insufficiently studious or energetic, he wants to debut with a first-class organization as one way of showing his seriousness.

Courtesy of Politico

In addition to those below, it also seems there is a reporting deadline for cash that would cause problem were he not to delay past this point. Something to do with the election laws. I suspect having to deal with this stuff may have changed his mind on McCain-Feingold.