It's not the long primary that has sucked enthusiasm out of the race, it's the front-runner:
[I]t's hard to imagine what sort of messaging would have worked better for Romney, especially considering his record. One of the arguments the consultants make elsewhere is that Romney hasn't captured the conservative media. … A little more outreach might have softened the skepticism, but it also might have illustrated how little Romney likes to be challenged on questions about his policy decisions, and how slippery he can be when anyone tries to pin him down. Romney isn't struggling because of his campaign. The campaign is struggling because of Romney.
Jim Antle adds:
Sure, I've been puzzled as to why the Romney campaign hasn't anticipated obvious lines of criticism or why they seem intent on irritating conservatives by boasting of the likelihood they will win a nomination they should have already had in the bag by now. But the candidate is a bigger problem than the campaign. Campaigns matter, sometimes a lot. But they matter less than political consultants think they do.
(Photo: Former Massachusetts Gov. Mitt Romney speaks to Sprint President and CEO Dan Hesse during the driver's meeting prior to the start of the NASCAR Sprint Cup Series Daytona 500 at Daytona International Speedway on February 26, 2012. By Chris Graythen/Getty Images)