No. Crist is too liberal to offer any help to McCain.
Which pretty much guarantees McCain will pick him. McCain is like Caesar—he has no principles beyond his personal dignitas. Conservatives have offended him, and therefore they must be punished and forced to bend the knee. McCain will pick the most liberal VP candidate possible to shame and demoralize conservatives to the maximum extent he can. He wants to know, and more importantly he wants you to know, that ever single conservative vote he gets was taken by force, not earned.