Sean Trende today makes a key point about assessing presidential nomination contests: “No candidate comes to an election with a perfect resume — certainly not Bill Clinton, certainly not George W. Bush, and certainly not Barack Obama.”

This frequently is overlooked. Many pundits were certain that Mitt Romney would never be nominated because his health-care record in Massachusetts would make him radioactive to Obamacare-hating Tea Party voters in Republican primaries, or because of his flip-flops on social issues, or because of his religion. Yet Romney won, and it wasn’t even close. Clinton also swept to an easy nomination despite scandals.

So how can we know how much baggage is too much? I don’t mean a liability that would be an absolute disqualification, which generally means policy positions far from the party’s mainstream. I mean scandals, gaffes, difficult to explain past positions.

The answer is that there are no hard-and-fast rules.

Remember, at this stage, we’re still talking about party actors during the invisible primary. (By party actors, I mean the large group of people that includes politicians, campaign and governing professionals, formal party staff and officials, donors and activists, party-aligned interest groups, and the partisan media.) Some have more influence than others, but they all care deeply about the nomination and won’t simply decide at the last minute based on who has the shiniest TV ad.

Some will care most about finding the candidate most likely to win. Some will put more emphasis on ideological orthodoxy. Others will care about a single narrow policy area. Others will think of this stage as akin to picking a factional leader, regardless of whether that person is well-situated to win even the nomination. And others will care about how the candidates would govern if elected — whether they are equipped to succeed, and whether they would be easy to work with.

Trende wrote about Christie, and I think he is correct that the New Jersey governor remains a contender. But the bridge scandal risks undermining him in many of the areas in which he might be judged. That isn’t just a matter of the scandal’s immediate effect on voters, which might say something about his electability. Party actors also have to judge if more scandals are likely, and also decide what the scandal tells them about working with him if he wins, and about how well he might govern.

Christie’s biggest challenge is that the party actors who are drawn to him in the first place are those most likely to care about such questions. After all, his main supporters were never going to be the guardians of ideological purity.

Compare that with Romney in 2012 and John McCain in 2008. Their chief problem was that they couldn’t calm the fears of ideological party actors. But Romneycare and McCain’s campaign-finance bill and their other violations weren’t particularly large problems for their core support among party actors. All they needed to do was to grovel enough that ideological conservatives and single-issue supporters wouldn’t try hard to veto them. Christie faces a very different problem.

That doesn’t mean Christie is necessarily sunk, at least if nothing more devastating is revealed by the investigations of Bridgegate. Candidates with plenty of baggage can, and do, win nominations . But this does show why this particular scandal is such a big deal for Christie.

[Cross-posted at Bloomberg View]

Jonathan Bernstein

Jonathan Bernstein is a political scientist who writes about American politics, especially the presidency, Congress, parties, and elections.