Tropical Storm Isaac had just delayed the Republican National Convention when a new menace hit the GOP: Hurricane Charlie Crist.

The former Republican and former governor waited until the Sunday before the Tampa convention to pen an op-ed in the Tampa Bay Times that officially cast his lot with President Obama.

It was yet another sign that Crist — now an independent — is expected to join the Democratic Party. It also positions him for a speaking slot at the Democrats’ convention next week as well as a run for his old seat against Republican Gov. Rick Scott in two years.

But Crist also carries baggage that could weigh down the power of his endorsement as well as his future political ambitions. Republicans quickly howled that Crist is a “crass political opportunist” and isn’t so much a storm threat as a gust of hot air.

Indeed, Crist was a storm force in Florida politics. But he’s also a political weathervane.

Right now, though, the op-ed is clearly a coup for the Obama campaign. Democrats can crow that Crist’s support is a bellwether of independent-minded voters in Florida and a repudiation of today’s Republicanism.

“Across Florida, in Washington and around the country, I've watched the failure of those who favor extreme rhetoric over sensible compromise,” Crist wrote, “and I've seen how those who never lose sight of solutions sow the greatest successes.”

Yet Crist is a flawed messenger when it comes to talking about achievements.

His term as governor from 2007 to 2011 was characterized by the worst recession since the Great Depression and an inability to square his self-described optimism with the pain of everyday Floridians.

Crist’s health-insurance plan failed to expand affordable healthcare. His tax-cut plans failed to boost the economy. People lost their homes and jobs in droves. He proposed a public-works building program that busted before it turned dirt.

Amid rampant job loss, Crist couldn’t articulate any concrete plans to boost employment. Instead, he visited unemployment centers and talked about job losses. He advocated for President Obama’s stimulus package and unemployment benefits, but the hope of turning the economy around faded.

What’s more, Crist had a schedule that sometimes appeared light on governing and heavy on time off, politicking or travelling. He took an average of 10 weeks off a year.

Then, when a safe-looking U.S. Senate seat came open in 2010, he preferred to leave the governor’s mansion in Tallahassee for a seat in Washington.

But the bad economy and Crist’s literal embrace of Obama and the stimulus cost him. Former House Speaker Marco Rubio started beating Crist so badly in the Republican primary that Crist left the GOP after repeatedly saying he wouldn’t. He lost in the general election.

Crist’s hand-picked Republican Party of Florida Chairman, Jim Greer, had tried to help Crist’s Senate campaign but was later charged with fraud. Greer says he’s not guilty, was set up by Rubio-loving Republicans and was abandoned by Crist.

Crist will now say the party left him, that he didn’t leave the party. But it only happened when an election was on the line. And it proved that a third-party candidate can’t win statewide in Florida.

Now, another election in 2014 looms and Crist could make yet another switch — from independent to Democrat.