So liberals have already started their attacks on Joe Miller (h/t to Andrew Sullivan.) If that is the best they can do, he should be fine in a Republican-leaning state in a Republican-leaning year - as long as it stays a two person race.
It seems like Lisa Murkowski might be thinking of going the third party route. It is tough to imagine a rationale for her campaign. I guess she could cobble together some kind of pro-choice, pro-pork, pro-seniority platform. It would clearly just be a Charlie Crist-like attempt by a hack politician to hold on to office for the sake of holding on to office.
Even though the polls are all over the place, I don't expect Crist to win in Florida. Rubio's message is a little overwrought for me, but he is a well above average speaker, seems to have a clue on domestic policy, and will have plenty of money to get his message out. With Crist's movements to the left on abortion and Obamacare, Rubio should be able to consolidate the right-of center vote. It would take a major Rubio scandal and/or virtually unanimous tactical voting from usually Democratic voters for Crist to win.
It is interesting to compare Crist and (maybe) Murkowski with the Democrat-affiliated independents in the Senate. Lieberman broke with his party over differences with his party's base on a high salience issue. Bernie Sanders is an explicit social democrat and the Democrats (an internally complicated party) tend to furiously reject that label. Their formal estrangement from the Democratic Party is based on stuff that matters. What, other than ambition, estranges Crist or Murkowski from the Republicans? Does anyone doubt that Crist would take back his support of the stimulus and the Obama hug if it could be guaranteed he would get the Republican nomination and a two man race against Kendrick Meek or that Crist would still be pro-life and pro-repeal of Obamacare if he was the Republican nominee?