Alexandria Ocasio-Cortez, the 28-year-old New York socialist who rose to political stardom by championing far-left policies such as abolishing ICE and pushing a federal jobs guarantee on her way to an upset primary win, is headed to Missouri to help topple another incumbent Democrat.

Ocasio-Cortez will be campaigning in St. Louis for Cori Bush, a fellow activist running as a Justice Democrat with hopes of defeating incumbent Democrat Rep. Lacy Clay, a member of Congress since 2001, in an August primary.

The visit poses an obstacle for Sen. Claire McCaskill (D.), who entered the Missouri legislature the same year as Clay and has maintained a friendship with him for more than three decades since. Despite her relationship with Clay, and her stated belief that ideas such as abolishing ICE are "dumb," McCaskill has been unwilling to get behind Clay.

Clay told the St. Louis Post-Dispatch he considers McCaskill a "supporter," but the senator has refused to endorse him in his race against Bush, with her campaign saying she doesn't get involved in Missouri Democratic primaries.

McCaskill's refusal to back Clay as he attempts to stave off the challenge from the party's more liberal wing comes as many reconsider their embrace of Ocasio-Cortez, who was quickly anointed the "future" of the party by DNC chairman Tom Perez following her election win.

In the weeks since, Ocasio-Cortez has fanned the flames on her battle with the party's establishment, causing some House Democrats to complain about her tendency to make "enemies" with fellow party members and her "lack of maturity." She also embraced socialism and exhibited a blatant lack of understanding of foreign affairs during an interview with Margaret Hoover of PBS, causing even CNN's Chris Cillizza, who himself celebrated Ocasio-Cortez's potential, to caution Democrats to "maybe slow their roll on pushing Alexandria Ocasio-Cortez as their next big star."

"The problem is that, prior to June 27, almost no one outside of New York's 14th District knew who she was," Cillizza wrote. "And that, in the following month, very few people who fully embraced her have really done any sort of deep dive into what all she believes."

Former Democratic senator Joe Lieberman urged Rep. Joe Crowley, the Democrat defeated by Ocasio-Cortez, to mount a run to save his party from her radical views, which he said would "bankrupt the country."

"For the sake of Congress and our country," Lieberman wrote, "I hope Joe Crowley will give all the voters of his district the opportunity to re-elect him in November—and I hope they find his name on their ballots."

McCaskill did not respond to a request for comment on Ocasio-Cortez's visit to Missouri this weekend.

McCaskill's reluctance to write off Bush's nomination could be due to criticism from African-American leaders in the state.

Bush, an African-American woman who gained prominence in Missouri during the protests over police brutality in Ferguson, is supported by African-American leaders in the state such as state representative Bruce Franks, who laid into McCaskill earlier this year for her failure to reach out to his community during her time as senator.

"I’m going to vote for Claire, but Claire is going to have to bring her ass to St. Louis," Franks said.

McCaskill responded to the criticism with an attempt to rally support from Clay and other African-American politicians for a letter pushing back on Franks, but nobody agreed to sign it.

"I'm 100 percent certain that nobody signed it," said Missouri representative Emmanuel Cleaver (D.). "We talked about it very seriously and strongly and every one of us said, ‘We’re going to support her, but signing this letter isn’t going to achieve what she wants. It’s just going to make people angry.'"

McCaskill said she understands the reluctance to sign the letter and will not take her supporters in the black community for granted.

"I think maybe the letter elevated the issue maybe more than it should have been and it was fine," she said. "I mean, listen, here's the bottom line: I am going to work very hard and not take one vote for granted. I am blessed to have a lot of friends and a lot of supporters in the black community and I am not going to take one of them for granted."

"I try to be the kind of senator who listens and responds to the needs of the African-American community," McCaskill said.