Violent crime levels have dropped significantly in the first half of the year, according to a new report from the Major Cities Chiefs Association.

Overall, violent crime dropped by 6 percent and homicides fell by 17 percent in 69 cities compared to the same period last year. Columbus, Ohio, saw the biggest drop in violent crime at 41 percent, according to an Axios data analysis. But cities including Miami, Washington, DC, and Austin, Texas, also saw large declines. Notably, New York City was not included in the data, though other reports have indicated that violent crime is falling there, too.

It’s hard to say exactly what’s causing the decline, which comes after a major Covid-19 crime wave. It may be partially due to policies aimed at tackling crime at the federal, state, and local levels. But it may also just be a symptom of the fact that normal life in America has resumed post-pandemic — or a combination of those and other factors.

Republicans have long tried to use concerns about crime as a political cudgel against President Joe Biden’s administration. While former President Donald Trump doesn’t appear to be giving up on that attack strategy just yet, Democrats can now use the new data as a defense. Whether that will be effective, however, is far from certain.

In a statement on Saturday, President Joe Biden credited the $1.9 trillion economic stimulus bill that Congress passed in 2021, which allocated $15 billion toward public safety and violence prevention efforts, for helping bring down crime levels. He also cited bipartisan gun control law that expanded background checks and encouraged states to adopt “red flag” laws to prevent people who pose a danger to themselves or others from obtaining a gun.

But while those laws may have helped, some experts are highly skeptical of attributing the decrease to specific government initiatives.

“I think it’s early to know exactly why murder and violent crime are going down now,” said Jeff Asher, a crime researcher who runs a crime database at AH Datalytics. “Generally, I’m skeptical of political actions causing crime to go up or crime to go down, especially at the federal level.”

However, the pandemic crime was such an outlier in terms of the speed and degree to which it took hold that Asher said it’s possible that government spending on public safety helped interrupt such an acute increase in violence.

Other social and psychological factors may have also contributed. Anna Harvey, a crime researcher at New York University, said that there is a “robust body of evidence” showing that violent crime is often driven by emotion, such as stress or anger, as well as opportunity and the threat of getting caught.

“The Covid pandemic appears to have directly increased levels of stress potentially contributing to higher rates of violent crime during the pandemic period and decreasing levels as the pandemic abated,” she said. “The pandemic also affected the probability that violent crime would be observed by others and reported to the police, affecting the ‘Will I get caught?’ aspect of decision-making.”

She said the probability of getting caught went down given that foot traffic in cities sharply decreased and recovered slowly during and after the pandemic, with many choosing to work from home or move away from cities. Using cellphone location data, researchers at the University of Toronto found that the downtowns of many northern cities in particular struggled to return to pre-pandemic levels of activity through at least November 2022.

“The trend is a gradual recovery in foot traffic, mirroring the gradual decrease in violent crime rates,” Harvey said.

This year, crime may not rank as the top issue on most voters’ minds. Similar shares of voters — between 1 and 4 percent — said crime was the most important issue facing the country in Gallup surveys every month this year, even as crime went down. But it’s still a big concern: In a March Gallup poll, 53 percent said that they worry a “great deal” about crime and violence.

Trump has sought to capitalize on that by linking Harris, a former federal prosecutor and attorney general of California, to the movement to “defund the police.” He’s also campaigned by stoking fear about the criminal threats posed by undocumented immigrants, linking the issue of crime to Biden’s unpopular handling of the US-Mexico border.

Harris has pushed back against those attacks, recently releasing a new ad identifying her as a former “border state prosecutor” who has spent “decades fighting violent crime.” Trump’s attacks related to immigration also just aren’t based in fact: Unauthorized border crossings have been declining for five straight months and have returned to levels not seen since Trump was in office. FBI crime data also shows that border cities tend to have some of the lowest levels of crime in the country. And other research has shown that US-born citizens are more than two times more likely to be arrested for violent crimes than undocumented immigrants.

That doesn’t necessarily neutralize the political threat posed by Republican attacks claiming Democrats are weak on crime. Public perception often lags behind the stats, and it may be difficult for the party to change opinions after the Covid-era crime wave. But the next time Trump claims crime is out of control, the Harris campaign will have new evidence to point to.