Stuart Rothenberg warns against Republican overconfidence:

“We certainly have the wind at our backs now,” one veteran Republican consultant told me recently. “But as Scott Brown proved, two or three weeks is a lifetime in politics. Eight months is several political lifetimes.”

Polls, pollsters are fond of pointing out, are nothing but snapshots of current sentiment. Right now, those snapshots look excellent for the GOP. But does anyone really believe that Republicans aren’t capable of screwing things up?

Well, he’s got a point there. As he observes, a dramatic uptick in the economy and employment, eccentric primary choices (e.g., Rand Paul in Kentucky, endorsed by Sarah Palin, but favoring his father’s extreme isolationism on foreign policy), and an arrogant tone can all impede Republican gains. But let’s be frank: when a party is warned about “overconfidence,” things are going pretty well. It is a rare election season when Republicans lead in the generic congressional polling. And at least two Senate seats (Delaware and North Dakota) have all but been written off as losses by the Democrats.

Republicans would do well to keep in mind what worked and what didn’t in New Jersey, Virginia, and Massachusetts. In all three, the candidates ran on a conservative economic platform that opposed big-government legislation and the backroom deals that begat that legislation. But not one of these candidates engaged in harsh personal attacks on Obama himself. All three were rather polished debaters who could parry and thrust with their opponents and who were able to pin them down on specific positions on taxes and, in the case of Scott Brown, the war against Islamic fascists. Two were pro-life candidates who did not hide their records, and all three refused to be drawn into divisive, distracting arguments over hot-button issues by both their opponents and their opponents’ handmaidens in the media. And frankly, all three were cheery, likable candidates. Curmudgeons and yellers make for good cable-TV and radio talk shows, but rarely do they make effective candidates, especially in states where it is essential to draw from independents and Democrats to form a winning coalition of support.

So Rothenberg is right: there is plenty of time for Republicans to blow it. If they fail to field adept candidates or get distracted from an effective Center-Right message, Republicans will find the wave election of 2010 to be little more than a ripple.