National Journal's John Mercurio points out that Florida's Senate race has already undergone one drastic swing:

As we await final word on the future of Florida Gov. Charlie Crist (R?), consider this glaring piece of irony: Crist's decision on whether to bolt the GOP and run for Senate as an independent is driven in part by polls suggesting that his prospects brighten dramatically in a three-way vote. But the election is still more than six months away. And six months ago, similar polls showed Crist sporting supposedly "insurmountable" leads in the GOP primary over some nobody named Marco Rubio.

Is anyone reminding Crist of that reality today? Maybe so, which would explain why we've been treated this week to a fresh round of pre-bituaries of Crist's political career.

Perhaps Crist should keep that in mind as he decides whether or not to leave the GOP and run as an independent. Right now, things are looking terrible for him--he trails his Republican primary against Marco Rubio by over 20 percentage points in major polls--but a lot can change in six months. The GOP primary date is August 24.

One thing to keep in mind: Rubio is reportedly being investigated by the IRS in connection with the Republican Party of Florida's scandal over party credit cards. The U.S. Attorney's office in Tallahassee, the FBI, and the IRS are involved in an investigation of three credit cards total, one held by Rubio.  Rubio has acknowledged that he double-billed state taxpayers and the Florida GOP for several plane flights, and he has said he would pay back the $3,000. The investigation apparently will examine whether or not Rubio's expenses constituted income, and whether he should have paid taxes on them. His tax attorney says they didn't, and that he's in the clear. [UPDATE: The Rubio campaign says Rubio has not been contacted about any investigation.]

Crist's campaign has been beating the credit-card drum, but to no avail. Card statements will be released sometime in the next week and a half by the Florida GOP, which has launched its own investigation. If Crist thinks anything damaging will come out on Rubio, that would form an incentive for him to wait it out and keep running in the GOP primary. If anything borderline-damaging is unveiled--e.g., any personal expenses that haven't already been reported--they will likely pale in comparison to the excesses of former Florida GOP Chairman Jim Greer and some of the party's other cardholders.

A massive credit card revelation seems like the best chance for this race to change overnight. Barring that, Crist would have to hope six months is enough time to reverse a 20-point deficit.

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