Besides the Harris campaign and its affiliated political action committees, few economic or political sectors placed larger bets than organized labor on Vice President Kamala Harris’s winning the presidency.

And few might reap more consequences from the incoming Trump administration. For public-sector unions that represent government workers, the threat is institutional and existential: Top advisers to President-elect Donald J. Trump want to eliminate them outright.

For service industry unions that represent hotel and restaurant workers, the threats may be to the members themselves: vulnerable and low-paid workers, often immigrants, who could be swept up in Mr. Trump’s promised mass deportations.

And for the leadership of the old-line industrial unions, the threat is from their members, many of whom ignored the pleadings of their leadership and voted for Mr. Trump.

“We do understand we have issues that are confronting us, major issues,” said Lee Saunders, chairman of the A.F.L.-C.I.O.’s political committee and president of the 1.6-million-strong American Federation of State, County and Municipal Employees. “This is going to impact the entire labor movement.”

Unions poured nearly $43 million into the Harris campaign, according to Open Secrets, but that understates the resources they put into phone banks, canvassing operations, education and persuasion efforts with their members and outreach to nonunion working-class households.