Many Democrats failed to turn out to vote at the rate they did in 2020 when they ousted Donald Trump, according to an analysis of election data.

Voters in liberal strongholds across the country, from city centers to suburban stretches, failed to show up to vote for Vice President Kamala Harris at the levels they had for Joseph R. Biden Jr. four years earlier, contributing significantly to her defeat by Donald J. Trump, according to a New York Times analysis of preliminary election data.

The numbers help fill in the picture of Mr. Trump’s commanding victory, showing it may not represent the resounding endorsement of his agenda that the final Electoral College vote suggests. Mr. Trump won the White House not only because he turned out his supporters and persuaded skeptics, but also because many Democrats sat this election out, presumably turned off by both candidates.

Counties with the biggest Democratic victories in 2020 delivered 1.9 million fewer votes for Ms. Harris than they had for Mr. Biden. The nation’s most Republican-heavy counties turned out an additional 1.2 million votes for Mr. Trump this year, according to the analysis of the 47 states where the vote count is largely complete.

The drop-off spanned demographics and economics. It was clear in counties with the highest job growth rates, counties with the most job losses and counties with the highest percentage of college-educated voters. Turnout was down, too, across groups that are traditionally strong for Democrats — including areas with large numbers of Black Christians and Jewish voters.

The decline in key cities, including Detroit and Philadelphia, made it exceptionally difficult for Ms. Harris to win the battlegrounds of Michigan and Pennsylvania.

The drop-off is an extraordinary shift for Democrats, who, motivated by Mr. Trump’s surprise victory in 2016, had turned out in eye-popping numbers for the three subsequent elections. They clipped his power in Washington in 2018, removed him from office in 2020 and defeated many of his handpicked candidates for battleground races in 2022.

Democrats said they need a new way to re-engage voters who are fatigued by the anti-Trump message and distrustful of both parties.

The reasons behind the drop-off are varied. For one, some backsliding could be expected after the record turnout in 2020, which was aided by pandemic rule changes that increased mail voting.

Some analysts point out that Ms. Harris was simply the latest political casualty of a postpandemic global trend favoring challengers, no matter the incumbents’ politics, in places like Japan, South Africa, South Korea and Britain.

But narrow results in swing states indicate that Democrats had an opportunity to turn back Mr. Trump once again. Some party officials said Ms. Harris did not have enough time to overhaul the campaign after taking over for Mr. Biden, whose popularity has plunged since his 2020 win.

Others were more critical of her messaging, suggesting the campaign was chasing ghosts in trying to appeal to Republican crossover voters by campaigning with conservatives like Liz Cheney and talking about threats to democracy. Instead, these people said, the Harris campaign should have spent more time talking about how her economic policies would affect an important, but disaffected, part of her party.

Structural differences between the Republican and Democratic operations may have played a role, too. The Harris campaign, flush with cash, relied on a traditional turnout program that stationed field staff members in campaign offices across the battleground map. To some degree, the data suggest that program worked; Ms. Harris won more voters than Mr. Biden in four of the six battleground states where the count is nearly complete. But that increase was swamped by Mr. Trump’s gains.

The former president seized on new federal election rulings that, for the first time, let campaigns directly coordinate with outside groups focused on pushing voters to the polls. Elon Musk, the world’s richest man, poured $175 million into canvassers for America PAC, whose team effectively took its marching orders from the Trump campaign.

“It’s really a question of playbooks,” said Donna Brazile, the former chairwoman of the Democratic National Committee. “Trump had edgier and stronger material that he was constantly communicating at rallies, on podcasts and in other appearances. Democrats tried to compete in seven battleground states and call it a day.”

Swamped in the Battlegrounds

In Pennsylvania, the biggest electoral prize on the battleground map, Mr. Trump’s victory received an outsize boost from an unlikely place — the five counties with the highest percentage of registered Democrats: Allegheny, Delaware, Lackawanna, Montgomery and Philadelphia.

Ms. Harris won these counties, but not by the margins needed to overcome Republican-heavy areas of the state. Total turnout was down from 2020 in all five Democratic strongholds, which could partly explain how Ms. Harris received 78,000 fewer votes than Mr. Biden. Mr. Trump added 24,000 votes to his total in these same counties.

This gap left Ms. Harris with little chance of winning Pennsylvania. Mr. Trump’s victory margin in the state, as of Sunday, was about 145,000 votes.

In Wisconsin, the voter participation rate overall was among the highest of any state. But voters in Democratic-heavy counties simply could not keep pace with gains from their Republican counterparts.

In the eight counties that include Milwaukee, Madison and the surrounding suburbs, Ms. Harris surpassed the Biden totals by about 20,000 votes. But Mr. Trump gained about the same. In the rest of Wisconsin, Democrats were drubbed.

In Michigan, Mr. Trump’s victory was mainly a result of the drop-off in Wayne County, home to Detroit and diverse suburbs like Dearborn and Hamtramck that supply the state with its most significant source of Democratic votes.

While Ms. Harris easily won Wayne County, she did it with 61,000 fewer votes than Mr. Biden had, a decline of about 10 percent, while Mr. Trump added 24,000 votes, a jump of about 9 percent.

That swing limited Ms. Harris’s hopes of winning Michigan, where Mr. Trump was ahead by about 81,000 votes.

Branden Snyder, a liberal organizer in Detroit, said he had conversations with other activists in the final weeks of the race about how strange they thought it was for Ms. Harris to bring Ms. Cheney, a former Republican House member from Wyoming, on the campaign trail in Detroit. Many progressive voters in the city viewed Ms. Harris as a centrist, he said, and they may have been better served hearing from a fellow liberal who could explain why they should be excited to support the vice president.

He said he vividly recalled realizing that Democrats were in trouble during the final weekend of the race when he was knocking on doors on the east side of Detroit and he could not find a way to persuade a middle-aged Black woman to cast her ballot. Black women have long been some of the Democratic Party’s most reliable voters.

“When you have Black women not voting because they say nothing is going to happen — that neither candidate is going to change anything — that is doomsday for Democrats,” Mr. Snyder said.

A Nationwide Trend

The warning bells are ringing for Democrats well beyond the battlegrounds. Ms. Harris won fewer votes than Mr. Biden in 36 of 47 states. (Results remained incomplete on Sunday in Alaska, Arizona and California.)

In predominantly urban counties nationwide where most votes had been counted, Ms. Harris received two million fewer votes than Mr. Biden had four years earlier. Overall votes in these counties were down by about 1.7 million.

The trend was especially striking in Cook County, Ill., home to Chicago, the nation’s third-largest city. Overall turnout there was down by 20 percent. Mr. Trump collected about his same 2020 total vote, but Ms. Harris’s total was more than 417,000 votes behind Mr. Biden’s.

In the nation’s suburbs, however, there was clearer evidence that Mr. Trump had successfully persuaded Biden voters to flip. Turnout in predominantly suburban counties held steady from 2020, but Ms. Harris drew about 940,000 fewer votes than Mr. Biden, while Mr. Trump added 1.3 million votes.

In counties where at least 40 percent of white adults hold a college degree, total turnout declined by about 230,000 votes, or 3 percent, from 2020. Ms. Harris won 271,000 fewer votes in such places, while Mr. Trump added 61,000.

In Texas, the party’s decade-long dream of turning it blue suffered a significant setback. While total turnout was about the same as four years ago, Ms. Harris won about 450,000 fewer votes than Mr. Biden. Mr. Trump enhanced his margin by 485,000 votes.

In New Jersey, where Democratic presidential candidates typically win by about 15 percentage points, Ms. Harris won by just five points. It was the narrowest margin in more than three decades, when then-Gov. Bill Clinton of Arkansas outlasted President George H.W. Bush by two percentage points.

This year in New Jersey, total turnout was down by about 442,000 votes, just shy of the decline of 475,000 votes for Ms. Harris from Mr. Biden.

Mr. Trump, once again, made gains despite a decrease in turnout, lifting his total in the state by 26,000 votes.