Kansas Republican Senator Pat Roberts' re-election just became even dicier.  Photographer: Bill Clark/CQ Roll Call via Getty Images
Kansas Republican Senator Pat Roberts' re-election just became even dicier.  Photographer: Bill Clark/CQ Roll Call via Getty Images

(Updates with court ruling in first, second and third paragraphs.)

Late yesterday afternoon, there was a big shakeup in what had been until now a pretty stable Senate election cycle: Pat Roberts of Kansas, who was already unpopular, became the the most vulnerable Republican incumbent senator when the Democratic nominee suddenly abandoned his campaign -- giving independent Greg Orman an opportunity to consolidate the anti-Roberts vote and perhaps win. (Secretary of State Kris Kobach ruled today that the Democratic candidate had to remain on the ballot. If the ruling is upheld, it would give Roberts an advantage, perhaps one that could not be overcome. This is headed to the courts, so we'll have to wait to find out what the Kansas Senate ballot will look like this fall.)

Despite the uncertainty, it's worth asking what would happen if Orman won the general. Who would he caucus with, the Democrats or the Republicans?

First, on the question of whether he could win: Regardless of the court ruling, Nate Silver’s first impressions -- that Orman would have an uphill battle, and that earlier polling suggesting he would lead Roberts in a two-candidate race should be severely discounted -- are probably correct. The chance of an Orman victory isn't zero, but I’ll wait for new polling before concluding that the earlier, hypothetical polls will be predictive (see also useful analysis from John Sides).

It’s harder to predict what would happen if Orman did win. There are good electoral arguments either way. If he goes with the Republicans, he’ll spend six years worrying about renomination, and with good reason: a Kansas Republican Party that almost bounced Roberts for being a RINO would be a serious challenge for an independent senator who would certainly be more moderate, and perhaps a lot more moderate. On the other hand, it’s not as if running as a Democrat would make for an easy re-election campaign. Indeed, the prospects for a long Senate career are so dicey that Orman might decide to just do whatever he thinks best, regardless of the consequences. Or not! It’s always a stretch to speculate about what a politician is thinking.

The one thing I would say with some confidence is that the pressures on Orman to eventually choose, and to wind up being essentially either a (moderate) Democrat or a (moderate) Republican, would be overwhelming. Partisan polarization in Congress isn’t just about the personal preferences of politicians, or even of constituents; it’s also institutionalized. Start with staff: there are plenty of people well qualified, for example, to be Republican or Democratic legislative directors, but there is practically no one who has learned how to be a truly independent aide. The same goes for every substantive position. Knowing whom to turn to for expertise, whom to trust … those are, on Capitol Hill, partisan types of knowledge. And staffers also value party loyalty, both because they are party loyalists, and because their Hill career paths require a record of party loyalty. Put it all together, and it’s no surprise that party-switchers usually have to replace their staffs, and then move sharply toward their new party’s median in their policy positions.

The only other thing we can say at this point is that if Orman now must function as a Democratic proxy, he will be pushed toward the Democrats. And at the same time, the party balance in Kansas should push him back the other direction. In electoral terms, right now, Orman will be trying to both act as the Democratic proxy (for Democrats) and the Republican alternative (for the fairly large number of Republicans who don’t like Roberts very much).

One of the oddities of this period of partisan polarization is that parties are strong in almost every way except when it comes to their place in the political culture. That keeps millions of people from admitting (to pollsters, and even to themselves) that they are strong partisans. That also probably is what makes it possible for the occasional independent candidate to run a strong race and sometimes even win (see, for example, independent Maine Senator Angus King). But the overwhelming centrality of parties kicks in soon enough, making governing as an independent pretty much impossible (see, for example, caucus-with-the-Democrats Maine Senator Angus King). Whatever Orman thinks, that’s the playing field he may be entering now.

To contact the writer of this article: Jonathan Bernstein at Jbernstein62@bloomberg.net.

To contact the editor responsible for this article: Max Berley at mberley@bloomberg.net.