One of the reasons — perhaps the most important reason — why Andrew Cuomo can’t and won’t be a serious candidate for the Democratic presidential nomination is his de facto support of the Independent Democratic Conference, the Pierre Laval-inspired faction that keeps the New York state Senate in Republican hands. In an illustration of why the DNC shouldn’t be in the business of crafting local messages, Keith Ellison didn’t get the memo:

The picture landed on Twitter innocently enough, one Bernie Sanders acolyte to another. “[email protected], great hearing about your awesome Harlem/Washington Heights district Senator Marisol,” tweeted Congressman Keith Ellison. The tweet accompanied a grinning selfie with Marisol Alcantara, a Manhattan state senator and fellow self-identified progressive. But the backlash on Monday came quick: more than 150 replies, most of them furious. “Congressman, you know that she caucuses with the Republicans, keeping them in power in the NY Senate despite a numerical minority?” asked Joshua Goodman, a former state senate Democratic staffer. Ellison is a leader in the national progressive movement, a deputy chair of the Democratic National Committee, and one of Sanders’s most prominent and vocal supporters. Alcantara is a former labor organizer and Sanders delegate. Together, they check every progressive box. Yet the congressman didn’t quite know what he had gotten himself into. Alcantara is one of eight Democrats who belong to the Independent Democratic Conference, a group of breakaway Democrats who have formed a power-sharing alliance with senate Republicans since 2013. For two years, the IDC even forced regular Democrats to remain in the minority when they had more than enough members, by party registration, to form a numerical majority with the IDC. While many of the IDC members self-identify as progressives and support liberal legislation, their existence ensures New York State will only move so far left.

To state the obvious, your nominally lefty ideological credentials mean nothing if you caucus with the IDC, and it’s doubly unacceptable when you represent a Manhattan district. Targeting every member of the IDC with the strongest primary challenge possible should be one of the very top priorities of New York Democrats, and no prominent national Democrat should support any one of these Republican stooges.

This blunder doesn’t mean that Ellison is a bad person or a bad choice to co-lead the DNC or not a Real Progressive or anything like that. Everybody screws up sometimes. But it is another object lesson that using “support for Bernie Sanders” as your primary criterion for determining someone’s lefty credentials is deeply silly.** (I should probably elaborate on this in another post, but given that a president can’t accomplish anything without substantial buy-in from most of the party, if the left can’t have a party without Bernie there’s never going to be a party in the first place.) And I would say that arguments that the choice between Perez and Ellison to lead the DNC was of near-apocalyptic significance* and the left should take its marbles and go home if the former wins haven’t worn well except that they were dumb in the first instance.

*I’ve said this before, but don’t you wish movement conservatives thought this way? “Well, Ford beating Reagan proves that we’ll never have any place in the Republican Party. Forget trying to win primaries, let’s try something that might really work, like a vanity presidential campaign to split the vote on the right in exchange for no benefits whatsoever every four years.” I don’t really get people who congratulate themselves on how quickly they’re willing to give up, but YMMV.

**I thought the first sentence of the graf made this clear, but since there’s some misunderstanding in comments, let me clarify that I’m not saying that Ellison is some kind of secret centrist. I like Ellison! He’s great, despite this mistake! My point is that Ellison’s mistake was to assume that Alcantara was a progressive because she supported Bernie. We can perhaps call this the “Tulsi Gabbard Fallacy.”