This is starting to look like it might happen:

Former Senate Majority Leader Howard Baker (R-Tenn.) is contacting powerbrokers in the Republican Party to build support for a 2008 presidential campaign by his one-time protégé, former Sen. Fred Thompson (R-Tenn.).
Baker, who Wednesday made a visit to the Senate, was asked by several Republicans about his involvement on Thompson’s behalf.
“He said, ‘I am making a few calls and I think it’s a great idea,'” said one Senate Republican who heard Baker discuss his efforts to advance Thompson’s prospects.
One Republican who discussed a possible bid with Thompson described his interest and Baker’s queries as “a friendly exploration.”
Baker is a close friend and mentor to Thompson. Thompson broke into national politics in a big way in 1973 when Baker named him chief Republican counsel on the Senate Watergate Committee. Thompson’s work helped to uncover the scandal that forced the resignation of President Nixon. Republicans believe Baker is coordinating efforts with Thompson, and view Baker’s emerging role as a sign that Thompson is taking steps toward launching a campaign.
Thompson has told allies in recent days that he is exploring seriously a bid for president in 2008 in response to what he has described as strong encouragement from Republicans dissatisfied with the current slate of candidates.
Thompson said one reason he is hesitant about running is his longtime friendship with Sen. John McCain (R-Ariz.). Thompson was one of only four Republican senators to endorse McCain’s 2000 presidential campaign and was an important ally in McCain’s effort to pass campaign-finance reform in 2002.
[…]
Rumors about Thompson running for president have filtered into Republican circles during the last several weeks. One lobbyist who recently asked Thompson about his plans said that Thompson merely smiled and replied, “I’m keeping my powder dry.”

This is excellent news and should shake up the campaign. Everyone thought this was all sown up and that we only had three choices, ha! Thompson shouldn’t bother worrying about McCain since he doesn’t stand a chance of winning the nomination, we don’t trust him anymore. Run, Thompson run. We need your warmth and appeal. We need your conservative values and your communication skills.