Sen. John Fetterman (D-Pa.) is under heavy fire from fellow Democrats for casting the deciding vote to advance Sen. Markwayne Mullin's (R-Okla.) nomination for DHS Secretary, with some openly calling for his ouster. Why it matters: The idea of trying to unseat Fetterman is never far from many Democrats' minds , but rarely has it been discussed so explicitly and so openly. "Once again Sen Fetterman shows why he is Trump's favorite Democrat. He needs to go," Rep. Brendan Boyle (D-Pa.), one of Fetterman's harshest critics, said in a post on X . Boyle, the top Democrat on the House Budget Committee and a rumored potential primary rival to Fetterman, has publicly criticized the senator before , but this was the first time he has expressed support for his removal. Fetterman's office did not respond to a request for comment on this story. What happened: Fetterman voted with Republicans on the Senate Homeland Security and Governmental Affairs Committee to advance Mullin's nomination to a floor vote. The vote was 8 -7, with all Democrats and Sen. Rand Paul (R-Ky.), the chair of the committee, voting against Mullin's nomination — making Fetterman the deciding vote. The Pennsylvania Democrat, first elected in 2022 as a progressive, has since stunned erstwhile allies by tacking to the right, staunchly defending Israel and extending frequent olive branches to the GOP. What they're saying: " If you needed any more proof that Fetterman has completely abandoned his constituents, here it is. Pennsylvanians deserve a Senator that actually fights for them," Rep. Pat Ryan (D-N.Y.) said on X. Rep. Chrissy Houlahan (D-Pa.), who had urged constituents ahead of the vote to call Fetterman's office and ask him to oppose Mullin's nomination, compared him negatively to Sen. Dave McCormick (R-Pa.) at a town hall Thursday night. "Well, we have this senator — we have two actually," she said to boos from the crowd. "And I have to be really honest with you, of the two I have more success in working with the one on the [Republican] side of the aisle than the one on the [Democratic] side of the aisle." Zoom out: It wasn't just sitting members of Congress tearing into the Pennsylvania senator. Former Rep. Conor Lamb, who was Fetterman's top Democratic primary opponent in 2022 and has remained critical of him, posted on X : "Did people think this vigilante was voting to protect their rights? Come on." Moe Davis, an unsuccessful 2020 North Carolina congressional candidate, even apologized to former donors for sharing his donor list with the Fetterman campaign. "I sincerely regret whatever part I had in helping to elect [John Fetterman] in 2022." The other side: "In January, I called on the president to fire [former DHS Secretary Kristi] Noem—and he did," Fetterman said in a statement defending his vote. "I truly approached the confirmation of my colleague and friend, Senator Mullin, with an open-mind. We need a leader at DHS. We must reopen DHS." Fetterman said his vote was "rooted in a strong committed, constructive working relationship with Senator Mullin for our nation's security."