Yes, Chris Christie has had a bad month, and it’s even possible that scandal will end his presidential campaign. Subpoenas are never a good thing.
But, no, the Republican presidential field for 2016 isn’t (as TPM’s Sahil Kapur claims) “slowly coming apart, tarnished by individual scandals as well as the struggles of some candidates to keep faith with the conservative base's stubborn rightward shift.”
A bit of perspective, please. Every presidential candidate – certainly including the last two Republican nominees, Mitt Romney and John McCain, and also Barack Obama in 2008 – has endured bad weeks. Or bad months. McCain basically endured a bad year. Those with longer memories will recall the brutal stretch Bill Clinton experienced at the start of the Democratic primaries in 1992, and how he nevertheless won the nomination easily and the presidency, too.
It’s true that any particular scandal or misstep could be decisive in the nomination battle. But for the candidates collectively, by definition, that can't be the case: One candidate is going to win.
More broadly: can we please, please, please retire this business of assessing the group of presidential candidates as a whole as if that's predictive of which party will capture the White House? The concept of “strength of field” matters a lot to the individual candidates as they fight for the nomination, but it doesn’t matter at all for the fall campaign in 2016. One candidate from each party -- not a field of candidates -- will contest the general election. It won’t matter, at that point, which losing candidates were brought down by scandal or by a perceived inability to keep faith with their party's base.
We don’t know yet which stumbles by various early-stage candidates will prove debilitating, and which won’t. We do know that many candidates who have been left for dead three years before the Iowa caucuses (or even three months or three weeks prior) have turned out to be remarkably resilient. And whichever candidates win the nomination will, by the time of the convention, have enthusiastic support from their parties.