“This is a campaign that is growing, expanding, and built to win this primary,” Mr. Rodriguez said in a statement. “We are ready to harness the energy of our thousands of grass-roots volunteers to phone bank, knock doors and turn out the vote for Kamala in these 2020 contests.”

In this race’s early stages, Ms. Harris showed all the signs of a possible coalition candidate, merging liberals and more moderate minority voters behind the strength of her historic bid to become the country’s first woman of color elected president. On the race’s first day, she raised $1.5 million, and she soon held a kickoff rally in Oakland, Calif., that remains one of the largest events for any candidate, with more than 20,000 people in attendance.

However, as the race has matured, Ms. Harris has been outflanked in money and ideology. Mr. Buttigieg has become the favorite of big money donors, and advisers for Mr. Biden, the race’s most prominent moderate candidate, are now considering a super PAC to supplement his coffers.

On the grass-roots side, progressives have centralized behind their two preferred candidates: Mr. Sanders, who retains many supporters from his previous presidential run, and Ms. Warren, who has grown her fund-raising base as her poll numbers have risen. She has outpaced Mr. Biden and Mr. Sanders in recent polls, both nationally and in a few early-voting states.

Ms. Harris’s team is adamant that she remains well-positioned — and adequately funded — to mount a vigorous operation in Iowa. As Mr. Biden’s poll numbers fade, Ms. Harris’s advisers believe her campaign is likely to gain from this and can use a strong initial showing to centralize black voters in later states. Recently, Ms. Harris shook up her senior staff, in a move that was first reported by Politico, and was taken as an acknowledgment of the campaign’s tough road ahead.