It’s a bad time to be a finance billionaire. Well, in Washington, D.C., anyway.

Republicans on Wall Street, who had been largely coalescing around former President Donald J. Trump’s efforts to return to office, suffered outright repudiation this week with his pick of Senator JD Vance of Ohio as a running mate. Mr. Vance, a harsh critic of corporate interests and a former venture capitalist, solidified a feeling in the world of high finance that the balance of power in the party had suddenly shifted westward to Silicon Valley.

In choosing Mr. Vance, Mr. Trump brushed off personal entreaties from some of the Republican Party’s biggest donors. Those financiers preferred Senator Marco Rubio of Florida, Governor Doug Burgum of North Dakota or Senator Tim Scott of South Carolina, all reliable supporters of traditional rightward causes like corporate tax cuts, freewheeling trade policies and internationalism writ large.

Mr. Vance, by comparison, has built a political brand as an antagonist of the financial elite by criticizing business tax breaks, talking up the costs of global trade, embracing cryptocurrency, and opposing diversity initiatives that are popular across corporate America.

While accepting his nomination on Wednesday at the Republican convention in Milwaukee, he said the party was done “catering to Wall Street.”

That line and several others in Mr. Vance’s speech cast Wall Street’s titans as villains. It was a clear sign to many financiers at the convention and those watching at home that the party is no longer a clear ally, according to interviews with nearly two dozen investors, ex-government officials and advisers to donors of both parties.