The New Yorker has an article that addresses this topic, called "The Cuban Strategy, Can Jeb Bush deliver the Florida vote in November?" by William Finnegan.Finnegan argues that Jeb Bush is very popular among Cubans (and other Latinos), but that his brother might not get the full benefit.
On-line, the New Yorker also has an interesting interview with Finnegan. He was asked: Is Florida up for grabs?
It does seem to be. Jeb Bush won reëlection as governor fairly easily in 2002, but he is popular among a number of groups that aren’t nearly as fond of his brother. Non-Cuban Latinos, for instance, tend in Florida (as elsewhere) to be Democrats. There are more than a million of them in the state—Dominicans, Mexicans, Nicaraguans, and, most numerously, Puerto Ricans. Jeb and his family have a strong cross-party appeal among these folks—Jeb’s wife, Columba, is from a small town in Mexico, and their son, George P., is a talented, attractive campaigner. Then, there’s Jeb’s fluent Spanish. But the war in Iraq has not been popular among these voters. Nor have the President’s tax policies or his economic management. Other groups who have tended to vote for Jeb, such as white veterans in the Panhandle (most of whom are registered Democrats), may vote for Kerry. Meanwhile, traditionally Democratic voters who still feel that the 2000 election was decided unfairly will be strongly motivated to go to the polls this year.The Democratic groups who might be especially motivated include African Americans (many were purged wrongly from voting rolls or intimidated by dubious election-day practices, and Palm Beach residents -- remember the butterfly ballot?). That last link is to a pdf file.
Finally, there are the Cubans, who are unlikely to vote for Kerry in very large numbers but who may not turn out heavily for Bush, either. Any significant incursion made on their support by the Democrats can certainly swing the election—when Bill Clinton got more than thirty per cent of the Cuban vote in 1996, he won Florida. There are more registered Democrats than Republicans in Florida, but that gap is narrowing. This election should be close.