On the night when Alexandria Ocasio-Cortez shocked the Democratic establishment by beating Rep. Joe Crowley in a primary in his Queens district last month, Crowley, a 10-term incumbent who had been considered a potential successor to Nancy Pelosi, grabbed his trusty guitar and dedicated a rendition of “Born to Run” to Ocasio-Cortez and her victory.

Less than three weeks later, those good feelings have turned into bad blood. The flashpoint: Crowley’s refusal to vacate his nomination from the progressive Working Families Party, something that will put him on the general-election ballot with Ocasio-Cortez and Republican nominee Anthony Pappas this November. On Thursday, Ocasio-Cortez took to Twitter to accuse Crowley of using the Working Families Party nomination to mount a third-party challenge:

.@repjoecrowley stated on live TV that he would absolutely support my candidacy.



Instead, he’s stood me up for all 3 scheduled concession calls.



Now, he’s mounting a 3rd party challenge against me and the Democratic Party- and against the will of @NYWFP.https://t.co/Xvb6Jk8N8q — Alexandria Ocasio-Cortez (@AOC) July 12, 2018

She sent out a subsequent tweet asking for donations. “So much for ‘Born to Run,’ ” she wrote. “If you want to see me in Congress, we need your help now more than ever. We cannot underestimate the power of dark money.”

Crowley, meanwhile, attempted to shrug off the controversy. “Alexandria, the race is over and Democrats need to come together,” he responded to her on Twitter. “I’ve made my support for you clear and the fact that I’m not running.” His staff later suggested to Politico that the missed concession calls were the fault of the Ocasio-Cortez campaign and claimed that her office called Crowley’s team on Thursday to admit the information she tweeted out was “a mistake.”

Ocasio-Cortez remains the prohibitive favorite in her deep-blue district with or without Crowley’s name on the ballot. Her GOP opponent has yet to report receiving a single donation, and her upset primary victory turned her into a folk hero on the left. So what explains Crowley’s decision to keep his name on the ballot while promising not to campaign?

According to Jerry H. Goldfeder, an election lawyer and an adjunct professor at Fordham University School of Law, the simplest answer is the state’s “extremely peculiar election laws.”

With the exception of extreme circumstances like death or moving out of state, a non–write-in candidate who wins a nomination can only be removed from the ballot if he or she accepts the same party’s nomination in another race, typically a lower-profile contest in another part of New York dominated by another party. The Working Families Party requested Crowley do just that after he lost the Democratic primary, but he reportedly refused. On Thursday, as Ocasio-Cortez’s complaint was gaining traction on Twitter, Crowley explained that he believes such a switch would be akin to “election fraud.”

I don’t plan on moving out of New York, have a clean record, hope God’s will is that I don’t die, and won’t commit what I honestly believe to be election fraud. https://t.co/Cxk3s5zALi — Joe Crowley (@JoeCrowleyforNY) July 12, 2018

Goldfeder said jumping races isn’t election fraud in the legal sense of the term but that the congressman’s logic makes sense. “He wants to avoid a fraud on the voters,” Goldfeder told Slate. “He wants to avoid the charade of running for another office [that he doesn’t want].” Goldfeder added that he sees no reason to suspect Crowley is plotting a third-party challenge against Ocasio-Cortez. “He’s endorsed her; he’s going to work for her,” Goldfeder said. “The district is going to elect her.”