Who knew? Charlie Crist is running for governor as a Democrat.

Perhaps the least-surprising announcement in Florida politics in years opens a primary run against Nan Rich and then a potential show down between the former Republican Gov. Crist and the current Republican Gov. Rick Scott.

Republicans have been preparing for this moment for many months and already have launched their first "don't-trust-Charlie" campaign ads. Democrats have been preparing for this moment for many months too, leaving Rich, the former state senator from Weston, wandering the state to convince people that she's the true Democrat running.

Props to my colleague, Orlando Sentinel columnist Jim Stratton, for seeing this day coming exactly three years ago, when Crist hit his low point, by badly losing the race for U.S. Senate to Republican Marco Rubio.

Here's what Jim wrote then for the Nov. 4, 2010, Sentinel:

       He's been one of Florida's most prominent and popular elected officials for more than a decade.
       Telegenic and earnest, with a shock of silver hair, a perpetual smile and, until this election, an uncanny feel for the state's political currents.
    But Gov. Charlie Crist, thumped in his campaign for U.S. Senate, now finds himself facing unemployment when his term ends in January.
       So what's next for the candidate who left the Republican Party to run as an independent?
       How about Democrat Charlie Crist?
       It's a long shot, but some fairly reasonable people say they wouldn't rule it out. Crist is a political survivor who's shown an ability to reinvent himself.
       Becoming a Democrat would be a dramatic step, but would it be any stranger than his metamorphosis from conservative Republican to pragmatic nonpartisan?
       "If he were to do that, it wouldn't shock me," said Scott Peelen, a longtime Crist friend and Republican. "I think his political life is far from done."
       Crist lost by 20 percentage points to former Florida House Speaker Marco Rubio. But he beat Congressman Kendrick Meek, the Democratic nominee, by 10 points -- and did so with no party infrastructure beneath him.
       Polls suggest he stripped significant Democratic support from Meek, an indication that Democrats both feared Rubio and found Crist's politics, for the most part, acceptable.
       Generally a social moderate, Crist endeared himself to Democrats early this year when he vetoed a controversial teacher merit-pay bill and a measure that would have required women seeking an abortion to first pay for and view an ultrasound. He also changed his position on gay adoption, saying he did not think the state should ban it.
       As a Republican governor, Crist gratefully accepted federal stimulus funds and famously -- or infamously -- gave President Barack Obama a half-hug when Obama came to Florida to promote the stimulus package.
       The gesture enraged conservative Republicans and tea-party activists -- and destroyed Crist's chances of winning the GOP primary. But it earned some goodwill among Democrats.