“I understand if you don’t want to talk about Florida, because his record on Florida is terrible,” Mr. Crist recently said of Mr. Scott.

To offset Mr. Scott’s fund-raising advantage, Mr. Crist is focusing on the grass roots, using Mr. Obama’s turnout strategies. Mr. Crist is now rolling out his money on television ads, which should blunt some of Mr. Scott’s attacks. He has also opened 25 field offices.

“Given the amount they have spent, we feel we are in a great position,” said Omar Khan, Mr. Crist’s campaign manager.

Rather than duck from his party switch, Mr. Crist and his supporters remind voters that he is a centrist who worked well with Democrats as governor and pushed for changes that sometimes scored him no political points, like making it easier for nonviolent felons to regain the right to vote.

“He did it because he knew it was right and he knew that we are always a country of second chances,” Mr. Clinton told a crowd that was largely African-American, a constituency that has lobbied the state about that issue, in a hotel ballroom here.

By now, the vast majority of Floridians know whom they will choose, analysts said. The fight will play out along the margins in certain swing counties, a pocket of Hispanics here, a group of Tea Party activists there.

The key to success in November for either candidate is turnout — something that analysts said would be easier for Republicans in this midterm election — and luring away independent voters, who make up 25 percent of the electorate. Mr. Crist also needs a large number of African-American and Hispanic votes.

“This whole shebang is going to depend on who shows up,” Mr. Clinton scolded the Democrats in the room. “In the end, it’s on you whether he becomes governor.”