Earlier today, I wrote about the ways Bernie Sanders's campaign has begun to paint the primary results as fundamentally illegitimate. It began with his comments about how states in the Deep South "distort" the who's ahead and who's behind in the vote. But it's ratcheted up tonight as Sanders faces a possible loss in New York that's partly driven by the fact that the Empire State, like many others, doesn't allow independents to vote in the Democratic primary.

"Today, 3 million people in the state of New York who are independents have lost their right to vote in the Democratic or Republican primary," Bernie Sanders said. "That’s wrong."

This is, arguably, a smart move for Sanders. He's about to run through a slew of contests — New York, Connecticut, Delaware, Maryland, and Pennsylvania — that limit the Democratic primary to registered Democrats. He's likely to lose those contests, and this helps him explain those losses away: he didn't lose so much as he was robbed by a Democratic Party establishment trying to protect its own.

It is, however, a cynical and perhaps dangerous move by Sanders. Convincing his supporters that these rules — rules which predate this primary — are illegitimate is going to make the campaign much more bitter, and reconciliation between the two camps much less likely. It's one thing, after all, to see your candidate lose. It's another to see the election stolen, and that's increasingly how Sanders supporters are understanding the race.

Sanders may have long held this view — Vermont has open primaries, after all — but he's not, to my knowledge, emphasized it in the past. He hasn't campaigned against closed primaries during his career in Congress, and neither he nor his supporters complained about disenfranchisement of independents when he won the closed primaries and caucuses in Alaska, Colorado, Kansas, Maine, Nebraska, or Wyoming.

Which isn't to say Sanders doesn't have a point. I prefer open primaries as well. But the rules of this election were set well in advance, and delegitimizing the outcome as a way to fire up supporters is a dangerous game to play.

Of course, Sanders is far from the only politician to opportunistically discover a deep opposition to the structure of the Democratic primary. In 2008, Hillary Clinton fought for Michigan and Florida's delegations to be seated after the two states, which favored her candidacy, violated Democratic Party rules and held early primaries.

Why Bernie Sanders's supporters are so angry about New York's primary rules