Thompson’s wife is urging him to run:

Close friends of Fred Thompson say his wife Jeri is urging him to take the plunge later this year and run for the Republican presidential nomination.

The former senator from Tennessee and current actor on “Law & Order,” in private conversation, makes it clear that he is seriously interested in launching a candidacy that has attracted extraordinary attention over the last two weeks. However, he does not plan to announce his candidacy in the immediate future.

The major rap against Thompson is that he was not a hard worker during his eight years in the Senate. His friends respond that this is an easily correctable error and that the same complaint was made about Ronald Reagan before he ran for president.

Thank you, Mrs. Thompson! It’s not easy to be on the campaign trail with small children, she is to be commended for sacrificing for her husband (so should Elizabeth Edwards, btw).
Good thing he keeps hinting that he’ll run so that we don’t turn our attention to other candidates who might lure us away.
Oh, BTW, I’m so glad that Michael Barone told Hugh Hewitt that it wasn’t too late for Thompson to enter the race:

HH: In your estimate, is it too late for a Fred Thompson to come in, given the organizational and money requirements of running a presidential campaign?

MB: No, I don’t think it’s too late. I mean, if you look at national polls of Republicans, the percentage of those not going for Giuliani, McCain, Romney and Gingrich has lowered from 32% in November down to 23% in March. But that’s still a quarter of the potential electorate sitting out there presently unmoored to any of those candidates. Gingrich, of course, may not run. That would put another 11% up for grabs. That says to me that you know, there are people around there looking, none of these candidates in the view of many sort of base conservatives is perfectly positioned on issues for that bloc of the electorate that you know, was really sort of the dominant bloc in many respects in the Republican races between 1980 and 2000. So there’s room there.

And who’s to say that the support for those candidates is firm? Maybe it’s pretty soft and will move to Thompson if he enters the race.
Maybe now Hewitt will stop saying that McCain, Giuliani and Romney are our only choices and it’s too late for another candidate to enter over the race.