In mid-2020, the country was reeling from a surge in violent crime and civil upheaval after the killing of George Floyd by the police — a knife’s-edge national crisis that President Donald J. Trump made a central issue in the run-up to Election Day.

Mr. Trump portrayed himself as the “law and order president” standing up to lawlessness, slamming “weak” liberals and calling demonstrators “domestic terrorists.” Joseph R. Biden Jr., who charted a centrist course on law enforcement as a senator, vice president and presidential candidate, vowed to address racial inequities in policing while standing behind the police as they battled the rising violence.

Four years later, the nation’s crime rates have shifted. The politics, however, have not budged.

Homicide rates are tumbling from pandemic highs in most cities, funding for law enforcement is rising, and tensions between the police and communities of color, while still significant, are no longer at a boiling point. But property crime, carjackings and smash-and-grab burglaries are up, adding to a sense of lawlessness, amplified on social media and local online message boards.

Mr. Trump is re-upping his blunt, visceral appeal to voter anxieties. He declared recently that “crime is rampant and out of control like never before,” promised to shoot shoplifters, embraced the “back the blue” slogan against liberal changes to police departments — and even falsely accused the F.B.I. of fabricating positive crime data to bolster Mr. Biden.

Mr. Biden, in response, is taking a more low-key approach. He has spotlighted improving violent crime rates, promoted vast increases in funding to law enforcement under his watch and pointed to an aggressive push on gun control, as well as a revived effort to hold local departments accountable for discriminatory and dangerous policing practices in Black and brown neighborhoods.

White House officials believe the numbers are decidedly on their side, even if in some cities rates of violent crime remain elevated from prepandemic levels. But for now, polls suggest the public is less focused on the areas of documentable progress than on the lingering problems — much like with the economy, where the cumulative impact of inflation overshadows a statistical improvement to standards of living.

“Unemployment is down, the economy is up, violence is down and the president’s got a 40 percent approval rating in the state of Michigan,” said Mike Duggan, the mayor of Detroit, where violence has dropped sharply over the last two years.

“It makes you wonder what the definition of success is,” added Mr. Duggan, a Democrat. His city’s homicide rate has declined 18 percent from January 2023 to January 2024.

In large measure, the pandemic-era rise in violent crime, which followed more than two decades of sharply declining crime rates, is attributable to factors beyond the control of presidents, or any other politicians. Increasingly, analysts see the volatile period from 2019 to 2024 as an anomaly — “a master class in criminology” showing how a mass disruption influences criminal behavior, said Adam Gelb, president of the Council on Criminal Justice, which analyzes raw weekly crime reports from 38 cities.

“I think it’s fairly easy to characterize what’s happened between 2020 and 2024,” Mr. Gelb said in an interview. “Violent crime went up and is now generally coming back down, while property crime went down and is now generally coming back up.”

People “cooped up with folks they had beefs with killed each other,” he added. The situation flipped when people began commuting again and businesses reopened, creating “opportunities” for property crime.

Murders — a bellwether for all violent crime — are down about 13 percent nationally from 2022 to 2023. Other serious crimes — sexual assault, robbery and assault — are also settling to their prepandemic levels in all but a handful of cities. Property crimes like theft, especially auto theft and shoplifting, are rising moderately from pandemic lows — and carjackings surged across the country, doubling from 2019 to 2023.

Mr. Biden, confronted with the spiking crime rate in 2021, prioritized law enforcement, making it a central focus of its economic recovery package, the enormous American Rescue Plan Act, which passed in 2022 without a single Republican vote.

“During his administration, there’s no doubt we have seen historic increases in the amounts of federal money going to law enforcement,” said Jim Pasco, executive director of the Fraternal Order of Police, the country’s largest organization of law enforcement officials, which endorsed Mr. Trump in 2020.

It is hard to track precisely how much of that money went to public safety (the White House claims more than $10 billion) because the rescue act was intended to rush cash out to local governments to compensate for lost revenue with a minimum of red tape. But the nonprofit news organization the Marshall Project estimated that about half of the first $52.6 billion used for revenue replacement had gone to agencies dedicated to criminal justice.

Cities and counties spent billions on the basics — payroll, bonuses to recruit and retain officers, new equipment — eliciting criticism on the left that the administration had leaned too hard into Mr. Biden’s fund-the-police mantra and was now bankrolling mass incarceration and improper surveillance.

But hundreds of millions of dollars have also been funneled into community-based programs intended to limit violence, police intervention and incarceration. A neighborhood-based anti-crime initiative in Detroit, which includes financial incentives for lowering crime rates, has played an important role in the city’s improving murder rate, Mr. Duggan said.

Analysts with the National League of Cities, which tracks rescue act spending, believe these initiatives — along with mental health, drug, anti-violence and homeless programs also funded in the rescue act — had taken pressure off overwhelmed departments, allowing them to focus on core crime fighting functions.

“It really helped, and we’ve heard that from city after city after city,” said Yucel Ors, the group’s legislative director for public safety.

Mayor Cavalier Johnson of Milwaukee said the infusion of cash helped his city deal with “a fiscal cliff” and leverage an increase in the sales tax to support police and fire departments.

“You’re not automatically going to drop off to prepandemic levels, but you gradually climb down from that, and that’s what we are seeing now,” said Mr. Johnson, a Democrat, whose city has experienced double-digit decreases in most types of crime over the past two years.

Nonetheless, polls suggest that many voters share some of Mr. Trump’s pessimistic views on crime: Most people believe lawlessness is on the rise, in a general sense, even if they say that things are not quite as bad in their own lives or neighborhoods.

Sixty-three percent of Americans said that crime was “extremely or very serious” in the country, while fewer, 17 percent, said the situation was deteriorating in their own neighborhoods, according to the annual Gallup survey on crime released in November. The trend is not new, but the overall sense that the country is spiraling out of control has intensified in recent years, spurred by the omnipresence of shocking accounts of crime on social media and hyperlocal neighborhood message boards.

Jeff Asher, a crime data analyst who closely tracks local trends, said it was “frustrating to have to keep arguing that the drop in crime is a real thing” when the decline in murders has been accelerating in the first few months of 2024, in some cities at a record-breaking clip.

Most categories of violent crime declined modestly in the first two-plus years of Mr. Trump’s term, but violent crime began spiking as the pandemic intensified into 2020, despite his claims that all the increases occurred on Mr. Biden’s watch.

Mr. Trump, like Mr. Biden, made law enforcement a priority — particularly when it came to immigration — and some funding included in pandemic relief packages passed on his watch made its way to local law enforcement. He also earned praise from progressives for enacting sweeping prison reforms through passage of the bipartisan First Step Act in 2018, and would go on to steer about $400 million to local departments to aid in hiring, among other initiatives.

But during the final months of his administration, he focused less on these accomplishments than on tone — expressing a willingness to stand up to protesters, and with the police. A White House fact sheet released in the summer of 2020 highlighted grants for law enforcement to address the protests in Kenosha, Wis., after the shooting of Jacob Blake, the deployment of federal agents “to save the courthouse in Portland from rioters” and an executive order proposing harsher penalties for destroying federal monuments.

Mr. Trump and his allies, then and now, have tried to tie Mr. Biden to progressive local officials who, for a time, de-emphasized prosecution of some nonviolent crimes to reduce incarceration rates. They have tied Democrats to the defund-the-police movement, even though none of the party’s top leaders, from the president on down, embrace that cause.

Democrats are now trying to turn the tables, calling out Trump allies who have proposed cuts to the F.B.I., the Justice Department and funding for the special counsel prosecuting the former president, Jack Smith.

In March, the Republican Study Group, the party’s policymaking arm, proposed eliminating a $416 million community policing grant program as part of a budget-cutting plan — which White House officials criticized as “a dangerous plan that would defund law enforcement.”

But the starkest difference, in terms of policy, between Mr. Biden’s tenure and that of Mr. Trump is how they have see the Justice Department’s role in addressing police violence against communities of color.

Under Attorney General Merrick B. Garland, the department has opened a series of so-called pattern-or-practice investigations, scrutinizing local departments whose actions have led to deaths or the abuse of citizens. They included police departments in Minneapolis after Mr. Floyd’s murder and in Louisville, Ky., after the fatal shooting of Breonna Taylor in her home by a specialized unit.

The department, under Mr. Garland, has used the process to reach far-ranging overhaul agreements between cities, police officials and community leaders. Such agreements had been largely abandoned during the Trump administration and would likely be scaled back sharply or ditched altogether if he was re-elected, officials said.

While many police officers tend to be conservative, Biden administration officials have gone out of their way to prod law enforcement officials to make changes without demoralizing or demonizing cops.

In early 2022, as White House officials raced to complete a sweeping executive order on policing in time for the second anniversary of Mr. Floyd’s death, police groups were enraged by some of the language in its introduction, especially a reference to “systemic racism” in the criminal justice system, which they viewed as unfairly broad.

After a series of intense exchanges, several administration officials — led by Vanita Gupta, the associate attorney general at the time — stepped in to rewrite the language while leaving in the substance of the proposals, including a call to revise use-of-force policies and to restrict chokeholds and no-knock warrants.

The intervention was significant to Mr. Pasco of the Fraternal Order of Police. He said it indicated that administration officials understood that tone was as important to his members as policies.

“I’ve always known Biden to be a very strong proponent of public safety, though I don’t believe that’s necessarily true for everyone in his administration,” Mr. Pasco said. “Now, will he get credit for that? He should, but who knows?”