Mr Crist, a populist governor in Florida with a history of bipartisanship, bolted from the Republicans on Thursday to run for the Senate as an independent. He did so only after it became clear he would lose his party's primary to conservative Marco Rubio.
No matter who wins a three-way race in Florida, the factors that drove Mr Crist from the Republicans are a microcosm of broader political and social changes contributing to polarisation.
"We have a deadlocked democracy," said Pat Buchanan, a conservative commentator and three-time presidential candidate. "Both parties, held hostage by their extremes, are incapable of tackling the issues that threaten this country."
Buchanan left the Republicans for the Reform Party after twice failing to win a presidential nomination.
Moderate senator Joe Lieberman of Connecticut left the Democratic Party after losing a 2006 nomination fight to liberal Ned Lamont. He won re-election as an independent.
Senator Arlen Specter quit the Republicans last year as he faced a conservative challenge in Pennsylvania. He found a home in the Democratic Party.
And now Mr Crist.
"Unfortunately our political system is broken," Mr Crist said in an appeal to independent-minded voters in Florida.
Democratic consultant Steve McMahon calls these voters the "invisible middle" because parties care far less about them than hard-core liberals and conservatives. This is especially the case in non-presidential election years like 2010, which tend to draw high percentages of partisan voters.
"Politicians are responding to the noisemakers of their party," said Mr McMahon, who helped engineer the 2004 presidential campaign of liberal Howard Dean. Mr Dean's unsuccessful campaign brought to light factors contributing to polarisation: new technologies and media. He launched his bid when the war in Iraq was highly popular. That was a political problem for the anti-war candidate until like-minded people began finding and organising through websites such as Meetup.org. Soon the anti-war minority became a vocal majority.
Now, to the explosion of blogs and the rise of partisan cable news channels, add the fact that the United States is a nation whose population increasingly get their information from people who agree with them. Facts become fungible. Compromise becomes cowardice.
Mr McMahon's firm recently conducted research showing most young voters get political information from Comedy Central's The Daily Show and The Colbert Report, mock news shows with a liberal bent.
"As a Democrat, that sounds great," McMahon said, "but as an American, that's scary, because a lot of them think those shows are news."
Another contributor is the fact both parties work to draw congressional districts so most lawmakers represent areas that are heavily Republican or Democratic. This is designed to protect incumbents but, as technology makes the practice more precise, it also favours hyper-partisan candidates.
Also fuelling the trend is money. Special-interest groups on both sides of the partisan divide – say, anti-tax groups on the Right and abortion-rights groups on the Left – raise the most money when there is a fight. So they pick fights.
Incumbents who cross swords with party interest groups find their fundraising drying up or even face a well-funded primary rival.
Record numbers of people tell pollsters they are independents. The public's approval of both parties is at an all-time low. Will more politicians follow voters out of the major parties?
Yes, said Mr McMahon: "There is a market for independent candidates that Joe Lieberman capitalised on and Charlie Crist seized, so there will be others who explore that market."
But is there a will or a way for compromise? In this political climate, is America willing – much less able – to make hard choices and sacrifice?
"It's much bigger than Florida. It's much bigger than politics," said McMahon. "It's what's happening in America."
Ron Fournier is Washington bureau chief for Associated Press.