The problem for Republicans is that Mr. Obama was a terrible fit for the state’s eclectic mix of white voters. The Florida Panhandle is full of the culturally Southern white voters who rejected Mr. Obama, as they did across Dixie. Mr. Obama also struggled with older whites over age 65, who represent 30 percent of the state’s white voters, and among Jewish voters, who represent about 15 percent of self-identified white Democrats in Florida. Mr. Obama’s strengths — like his appeal to young, socially progressive voters in well-educated metropolitan areas — lack pull in Florida.

All of this will be reversed if the Democrats nominate Hillary Rodham Clinton, who is a good fit for the state’s odd combination of Southerners, New York expats and older white voters. Mrs. Clinton doesn’t even need to outperform Mr. Obama among Florida’s white voters anyway, as she’ll benefit from four more years of demographic change.

As for the rest of the country, a Republican pathway to victory is extremely challenging without Florida’s 29 electoral votes. It could flip Ohio, Virginia, Colorado, Iowa, Wisconsin and New Hampshire and still fall short. To compensate, Republicans would probably need to win states like Minnesota, Michigan or Pennsylvania, which were not seriously contested in 2012 and have been out of the reach of Republican presidential candidates for a generation.