In Iowa, New Hampshire and South Carolina, turnout surged, compared to four years ago and each state went to a different candidate.

But that trend appears to be on the decline. In both Florida and Nevada, turnout dropped sharply from 2008. Florida saw nearly 280,000 fewer voters in its primary last week, while more than 11,000 fewer voters turned out to vote in Nevada on Saturday compared to four years ago. Mitt Romney won both states by a landslide.

Some observers say the declining interest is a reflection of the lack of enthusiasm for the former Massachusetts governor…

Some observers, however, point to a trend of higher turnout in counties where former House speaker Newt Gingrich outperformed Romney.

“He’s much more of an attack dog when it comes to not only his primary opponents but also his potential general election opponent, Obama,” said Michael McDonald, a professor at George Mason University who runs the United States Elections Project, which monitors election and turnout data. “The Republican voters really crave someone who’s going to display that sort of attack mentality when it comes to the general election. That’s something you can get enthused upon. Romney’s campaign is not a campaign that seems to be able to spark that kind of enthusiasm.”