Democratic Sen. John Fetterman has addressed the Republican midterm convention, escalating tensions with his party. His appearance is stirring fears among Democrats that he might switch parties after the midterms. Fetterman introduced Republican Sen. Dave McCormick in a video, calling him “a great American.” He criticized Democrats as extremists and expressed support for working with President Donald Trump. Fetterman said in a statement later Wednesday that he will not switch parties. He has been increasingly isolated from his party, supporting Israel’s war in Gaza and voting with Republicans on key issues. Democrats worry about his influence if they secure a narrow majority in the Senate.