Facing a surge in shootings and homicides and persistent Republican attacks on liberal criminal-justice policies, Democrats from the White House to Brooklyn Borough Hall are rallying with sudden confidence around a politically potent cause: funding the police.

In the nation’s capital on Wednesday, President Biden put the weight of his office behind a crime-fighting agenda, unveiling a national strategy that includes cracking down on illegal gun sales and encouraging cities to use hundreds of billions of dollars in pandemic relief money for law-enforcement purposes. His speech represented the most muscular response so far from his administration to a rise in crime that has stricken the country’s major cities.

In New York City, the country’s largest metropolis and a Democratic stronghold, it was Eric Adams, a former police officer who is Black, who rode an anti-crime message to a commanding lead in the initial round of the Democratic mayoral primary on Tuesday.

The back-to-back developments signaled a shift within the Democratic Party toward themes of public safety. Senior Democrats said they expected party leaders to lean hard into that issue in the coming months, trumpeting federal funding for police departments in the American Rescue Plan and attacking Republicans for having voted against it.

“This is not a time to turn our backs on law enforcement or our communities,” Mr. Biden said in his speech.

At the highest levels of the president’s party, there is a developing consensus that Democrats need to treat crime as an urgent political issue, and that they cannot allow voters to see the 2022 election as a choice between a liberal party that supports police reform and a conservative party that supports the police in the name of a broader law-and-order message.

Neither Mr. Biden nor Mr. Adams — nor other top Democrats — have backed away from efforts to reform policing or pursue racial-justice measures at the local and federal levels. Both men have melded rhetoric about fighting lawlessness with calls for an exhaustive reassessment of policing, and Mr. Biden has expressed hope that bipartisan talks on Capitol Hill will yield a landmark police-reform law.

In his speech on Wednesday, Mr. Biden also urged municipalities to spend federal funds on crime-prevention tactics besides policing, like youth programs and initiatives to absorb people released from prison into society.

A group of Congressional Black Caucus members are preparing to introduce legislation this week to fund violence intervention and work force development programs as part of an overall crime-reduction strategy, according to an aide.

But most Democratic leaders, from the president of the United States to the Brooklyn borough president, have also firmly rejected activist calls to slash police budgets and divert government resources toward other kinds of social services.

Mr. Adams has denounced that approach with open contempt, deriding “Defund the Police” activists as a collection of affluent whites and accusing a progressive rival, Maya Wiley, of focusing on left-wing sloganeering “at a time when Black and brown babies are being shot in our streets.”

That message evidently resonated with Black primary voters: Mr. Adams’s lead in the mayoral race was built on his popularity in the Bronx and working-class Black neighborhoods in Brooklyn that have been hit especially hard by a spike in murders and shootings. That may embolden Democrats who have held back from using law-and-order language for fear of alienating core elements of the party’s base.

Mr. Adams wasn’t alone. Three of the four top candidates in the election rejected calls to strip resources from the police, and diverse Democratic constituencies from Flushing to Flatbush appeared to reward them for it.

Republicans have already signaled that they plan to link Democrats with the “defund” movement next year, as they did in the 2020 campaign, and brand Mr. Biden and his party as more concerned with appeasing activists than locking up criminals. Conservative lawmakers in the House have been trying to scuff up Mr. Biden’s largely favorable image by depicting the country as being in the throes of overlapping crises around crime, border security and gas prices.

Representative Val Demings, a Florida Democrat who is challenging Senator Marco Rubio in 2022, said she believed her party was well positioned to rebut that attack. A former police chief in Orlando, Ms. Demings said she did not believe the party had to choose between pursuing changes to traditional policing and treating public safety as a paramount goal.

“The safety of our communities, the safety of our nation, is the No. 1 priority and the No. 1 concern,” Ms. Demings said, adding, “Everybody deserves to live in a safe community.”

Trying out a counterattack that could become a staple of Democratic messaging in 2022, Ms. Demings said that Republicans may have eagerly draped themselves in blue but had not followed up with concrete support for the police.

“When it came to supporting resources for local communities, including law enforcement, not one Republican voted in favor of that funding,” she said, alluding to the lock-step G.O.P. opposition to the Biden-backed American Rescue Plan. “When first responders needed them the most — one of those moments — they just didn’t deliver.”

It is not clear how universally Democrats will adopt that approach. While a majority of the party appears to welcome a message of being simultaneously tough on crime and stringent about police abuse, there is also significant resistance among liberals to policies that might bolster police departments, of which they are deeply distrustful.

Last month, a small group of House liberals briefly threatened to derail a bill to fund security at the Capitol complex, saying it was ineffective to keep supporting what they called “a broken system” rooted in white supremacy.

In New York, progressives were holding out hope that Ms. Wiley or another candidate could overtake Mr. Adams through the tabulation of ranked-choice ballots. That kind of upset is not entirely out of the question: Mr. Adams has alienated several of the other leading candidates with bitter personal attacks, and he faced serious questions about financial ethics and real-estate interests that fueled antipathy to his campaign. (If he prevails, national Democrats may come to find him an awkward ally on law-enforcement subjects and beyond.)

Some progressives were also looking beyond the five boroughs for encouragement, drawing satisfaction from a political upset in Buffalo, where the entrenched Democratic mayor lost to a socialist primary challenger who was a forceful critic of the city’s police department.

But in Washington, Democratic leaders are now plainly more preoccupied with heading off attacks from the right than on placating the activist left.

If this week has marked a highly visible turning point in Democratic politics, the party’s shift toward treating public safety as a central political concern has been a gradual one. Indeed, the coincidental overlap in Mr. Adams’s strong performance and Mr. Biden’s speech served to create a kind of artificially sudden climax in what was really a monthslong process of reshaping the Democratic message on crime and law enforcement.

As early as last November, congressional Democrats were engaged in a pitched debate over the impact of the “defund” movement on down-ballot elections. In the 2020 general election, Republicans savaged Democrats all over the country by linking them with the most strident faction of activists to emerge during a summer of racial-justice protests. Many Democrats were convinced the party’s candidates had suffered as a result, while progressives bristled at what they described as centrist scapegoating.

Two Democratic reviews of the campaign concluded that the party had not sufficiently pushed back on those attacks. One report, by a collection of Democratic advocacy groups including the centrist think tank Third Way, concluded that Republicans had weaponized the “defund the police” slogan with particular effectiveness “against candidates of color in swing districts with large white populations.”

By late spring of this year, the Democratic Congressional Campaign Committee was employing a more aggressive approach to answering Republican attacks. In a special election to fill a vacant House seat in New Mexico, Republicans were battering the Democratic candidate, Melanie Stansbury, for endorsing sweeping liberal legislation that would have reduced funding for police departments and placed stricter limits on law-enforcement authorities, among other progressive wish-list goals. With a crime wave buffeting Albuquerque, it was a potentially damaging attack.

But Ms. Stansbury and her national allies mounted a determined response, blanketing the Democratic-leaning district with ads promoting her votes in the New Mexico State Legislature to fund local law enforcement. She won the race by a huge margin.

In another special election, pitting two Black Democrats against each other for an open House seat in Louisiana, the victorious candidate, Troy Carter, deflected criticism from a more progressive candidate, Karen Carter Peterson, who accused him of being too supportive of the police.

Representative Sean Patrick Maloney of New York, the chairman of the House Democrats’ campaign committee, said he saw the party rejecting a “false choice between supporting racial justice and supporting public safety.” He said the elections in New York and New Mexico, along with Mr. Biden’s speech, showed that the “broad center of the Democratic Party” expected lawmakers to pursue both goals at the same time.

Mr. Maloney, who endorsed Mr. Adams on the eve of the mayoral primary, said he expected that Democratic lawmakers and candidates would increasingly showcase their support for the law-enforcement funding in the rescue package that Republicans opposed.

“We are the only party in Washington right now funding the police,” Mr. Maloney said, “even as we fight for important reforms and racial justice.”