Voter turnout numbers are pointing to a potential enthusiasm deficit for Republican presidential front-runner Mitt Romney.

In the four states to vote so far in the GOP nominating race, turnout has been strongest where people were energized to vote for somebody else.

In Florida, where Romney grabbed a commanding 46 percent of the vote this week, overall turnout was down significantly from four years ago. A county-by-county look at the Florida numbers shows that turnout was up from four years ago in counties where rival Newt Gingrich did well and down in counties where Romney dominated, according to Michael McDonald, a professor at George Mason University who runs the United States Elections Project to track election data.

Romney is winning, McDonald said, "but the fact that he's not really lighting a fire for these voters should be a warning sign for the campaign."