WASHINGTON — Their high-profile primary was over weeks ago, but tensions between Rep. Joe Crowley, D-N.Y., and victorious challenger Alexandria Ocasio-Cortez have reignited in a Twitter spat.

Ocasio-Cortez beat Crowley, a top-ranking House Democrat and local powerbroker, in a stunning upset in a primary late last month. Crowley quickly conceded to the 28-year-old progressive upstart and pledged to support her.

But on Thursday, Ocasio-Cortez publicly accused Crowley of "mounting a 3rd party challenge against me" because his name will still appear on the ballot in November as the nominee of the Working Families Party, a progressive party that had endorsed him.

She also asked supporters on Twitter to donate to her campaign, warning, "We cannot underestimate the power of dark money."

.@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 (@Ocasio2018) July 12, 2018

Crowley fired back on Twitter by denying the charge and reiterating his commitment not to run against her. "I've made my support for you clear and the fact that I'm not running," the veteran congressman said.

Alexandria, the race is over and Democrats need to come together. I’ve made my support for you clear and the fact that I’m not running. We’ve scheduled phone calls and your team has not followed through. I’d like to connect but I’m not willing to air grievances on Twitter. https://t.co/hxEeWEpI2O — Joe Crowley (@JoeCrowleyNY) July 12, 2018

At the center of the fight is New York's byzantine election laws.

The Working Families Party confirmed that it asked Crowley to withdraw his name from the ballot after he lost the primary, but Crowley has refused, since none of the ways to do so are acceptable to him.

Under state law, to give up his spot on the ballot, Crowley would either have to register to vote in a different state (he does have a home in the Virginia suburbs of Washington) or switch his candidacy to run for a different office that he has no actual intention of seeking or likelihood of winning, such as a county clerkship in a Republican-dominated area upstate.

The only other ways that a name can be removed from the ballot is if the candidate dies or commits a felony.

A Crowley spokesperson said the congressman found the idea of running for another office unethical and the thought of officially moving out of state unacceptable. The spokesperson, who declined to be named, also reiterated that Crowley will continue to support Ocasio-Cortez despite the attacks, which the spokesperson characterized as untrue.

Working Families Party of New York Director Bill Lipton was not satisfied with that answer.

"It is disappointing that Crowley has refused to vacate the Working Families Party ballot line," Lipton said in a statement. "The only remaining way for Crowley to do the right thing is to switch his residency to Virginia, where his family resides and his children already go to school. It would fix the problem he created in an instant."

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 (@JoeCrowleyNY) July 12, 2018

A spokesperson for Ocasio-Cortez did not immediately respond to a request for comment.