Democrats frequently point to New Mexico, where former Rep. Heather Wilson, who many conservatives despise, is running against Lt. Gov. John Sanchez, who is tacking to her right. If Wilson survives a rough primary, it's an opportunity to coalesce support from the right and middle of the GOP electorate. And Sanchez, a Hispanic Republican statewide officeholder, has potential appeal as well. Wisconsin is a state where a nasty, tea party versus establishment primary is already brewing on the GOP side. But one could also argue that the almost-certain Democratic nominee, Rep. Tammy Baldwin, could have benefited from a primary. Would it have been the worst thing in the world if Rep. Ron Kind, a more moderate lawmaker from the western part of the state, had run against her? If she would have beaten him, she'd have proved an ability to win over moderates outside of the liberal enclave of Madison. Had she lost, perhaps she was not the best nominee in the first place. One reason pundits point out primaries are costly is because they can force a frontrunner to spend valuable money before the general election. After all, the argument goes, if a candidate has to spend millions fending off a nuisance opponent, the campaign's warchest could be depleted by the time the fall rolls around. That's true -- to an extent. But when talking about the handful of swing-state races where control of the Senate will be decided, the powerful Super PACs and other outside groups could rival spending from candidates in some cases. In other words, even if a candidate ends up having to overspend in the primary, if the general election race is within reach, the money from allies will be there. Heeding the lessons of 2012, national Republicans are not using a heavy hand when it comes to endorsements. But that may be a distinction without a difference, because in many races, it is clear who the implied National Republican Senatorial Committee favorite is. National Democrats, on the other hand, have been actively endorsing. For her own part, Murray drew a contrast on Tuesday between contested GOP primaries' and contested Democratic primaries. But in Arizona, Don Bivens has been blasting DSCC-favored Richard Carmona as a D.C.-handpicked candidate. In Connecticut, Susan Bysiewicz isn't going to just let Rep. Chris Murphy march to the nomination. Overall, there's real risk in allowing candidates with unproven track records statewide to coast until the late fall, when it may be too late to correct their flaws. Primaries, while often bloody, nasty affairs, mean those flaws will be addressed earlier rather than later.