BALTIMORE — The outpouring of protests across the country has scrambled the contest for chairman of the Democratic National Committee two weeks before the vote, as party activists thrash out who should be the face of a newly energized party.

The surge of liberal activism in response to President Trump’s election has transcended the divisions that some Democrats feared would cleave the party after its defeat in November. But it has also injected volatility into a race for party chairman that had been shaping up as a straightforward proxy war between the candidates most closely identified with Senator Bernie Sanders of Vermont and Hillary Clinton.

Representative Keith Ellison of Minnesota, one of Mr. Sanders’s most prominent surrogates during last year’s primary race, and Thomas E. Perez, the former labor secretary who backed Mrs. Clinton and received consideration to be her running mate, have emerged as the leading contenders. Yet neither has secured the support of anywhere close to a majority of the 447 committee members who will decide the race, as other candidates did in the weeks leading up to prior votes.

This is partly because other hopefuls in a field that has swelled to double digits have yet to withdraw from the race. But it also owes to the genuine uncertainty about who can best harness the antipathy toward Mr. Trump, and lead a party that has been dominated by former President Barack Obama, former President Bill Clinton and Mrs. Clinton for more than two decades.