In a sense, the primaries are a lot like the NCAA basketball tournament: You know there are going to be some surprises. The odds of every favorite winning every game in the NCAA tournament are longer than a billion-to-one against. And yet, in the end, one of the front-runners usually wins. (Since the men’s tournament expanded to 64 teams in 1985, all but three champions have been No. 4 seeds or better.)

So be wary of grand pronouncements about What It All Means based on a handful of “surprising” developments. Is Scott Walker’s campaign off to an “unexpectedly” bad start, for instance? Maybe. (I wouldn’t be thrilled if I were one of Walker’s strategists. I’d also remind myself that we have five months to go before the Iowa caucuses.) Even if you grant that Walker is having some problems, however, it would be stunning if all the Democratic and Republican campaigns were doing exactly as well as pundits anticipated. At any given moment, some campaigns are bound to be struggling to meet expectations, or exceeding them.

Similarly, while one might not have predicted that Bernie Sanders would be the one to do it, it was reasonably likely that some rival would emerge to Hillary Clinton. It’s happened for every non-incumbent front-runner in the past: Buchanan for Dole; Bill Bradley for Al Gore.