Pennsylvania Sen. John Fetterman said Thursday he would leave the Democratic Party if it formally adopted a platform opposing US aid to Israel, calling such a move a “red line” following a House vote on legislation that sought to eliminate assistance to the Jewish state. 

Fetterman’s comments came after lawmakers defeated a measure to end US aid to Israel. Nearly all Republicans and a narrow majority of Democrats voted against the bill. 

“If they put that in our platform—no aid for Israel—and officially become the anti-Israel party, then yeah, that’s a red line for me,” Fetterman told NBC News on Thursday. “Democrats, we’ve always should support Israel. That’s our special ally, you know? In the only democracy in the entire region, that’s Israel. So I’m always proud to stand with Israel.” 

He also said he could not support a party that officially abandoned Israel. 

“It would be a problem for me if the Democratic Party officially says, ‘Israel is the problem, Israel doesn’t deserve to exist, and I’m never going to support aid, and I’m not going to call out Hamas and Hezbollah and Iran as terrorists, and they are the problem in the region,’” Fetterman said. 

Fetterman did not say whether he would join the Republican Party or serve as an independent if he left the Democrats. 

Such a move would not be without precedent. Sens. Joe Manchin and Kyrsten Sinema both became independents while continuing to caucus with Democrats before retiring at the end of their respective Senate terms. 

The debate follows a House vote Wednesday in which 103 Democrats supported an amendment by Rep. Thomas Massie, R-Ky., to cut off US aid to Israel. Republicans overwhelmingly voted against the proposal. 

The issue reflects broader divisions within the Democratic Party. Younger Democrats have become increasingly sympathetic to Palestinians rather than Israelis, and a recent Pew Research Center poll found that 71% of younger Democrats hold unfavorable views of Israel.