Democratic Sen. John Fetterman spoke to the Republican midterm convention via video Wednesday, an extraordinary escalation of the growing rupture between the Pennsylvanian and his party.

Fetterman’s decision is certain to stoke fears, already simmering among Democrats, that he will switch parties. Democrats need to pick up four GOP-held Senate seats in November to regain the majority. If Fetterman were to join the Republican Party, Democrats would need to pick up another seat to have control of the chamber.

Fetterman spoke for just over one minute in a recorded video introducing his fellow Pennsylvania senator, Republican Dave McCormick, whom Fetterman called “a great American.”

He didn’t criticize anyone by name but suggested Democrats are extremists, underscoring the message that Republicans are trying to drive home during their two-day rally in Dallas. The convention is meant to fire up the conservative base ahead of midterm elections, when the president’s party has historically lost seats.

“I’m always going to stand with America,” Fetterman said. “I’m always going to reject the extremes and socialism and that anti-American way of life.”

Standing in front of a steel mill, Fetterman said he “will work with President Trump to fight and defend the steel way of life.”

Fetterman has grown increasingly isolated from his party as he maintains staunch support of Israel’s war in Gaza and criticizes left-wing candidates who are members of the Democratic Socialists of America. He’s often gone his own way in the Senate, voting with Republicans to end last year’s shutdown, supporting several of President Donald Trump’s nominees and opposing efforts to end the war in Iran.

Fetterman has repeatedly said he wouldn’t switch parties because of his support for labor unions, LGBTQ rights and other issues held dear by the left.