From the Miami Herald:
Miami's Diaz-Balart won't seek Martinez's Senate seat - Politics AP -

"It was a great honor to be considered by Gov. Crist for appointment to the United States Senate," the Republican congressman says in a written statement released late Monday. "I thank him for his kind gesture of confidence. After giving the governor's request serious consideration and deliberation, I have decided to remain in the U.S. House of Representatives fighting for the causes which I deeply believe in."

Diaz-Balart has served in Congress since 1993 and would have had to give up a politically safe seat for a brief stint in the Senate. Crist is running for the Senate seat himself and it's understood that his appointment will bow out in 2010.
So what kind of situation does this put Crist in? With Martinez retirement Crist still has some time to go before the election. He wants the seat for himself but would look bad appointing himself. Also he would be required to vote before the election can be held and with him voting on some of the major issues coming up he can find himself in a jam with the moderates and also with the conservatives backing his primary opponent Marco Rubio. So now he has to appoint someone without ambition or who will be a weak pick. Tough spot. Discuss.