Ben Wofford is a researcher at Politico Magazine.

The mayors of America’s cities are deeply concerned about rising crime and homicide rates—and deeply frustrated with the Congress’ continued inaction on gun control amid a spate of mass shootings. Stronger gun regulation is needed right now, mayors say, and Congress has hung them out to dry. Senators and representatives “will not be able to escape responsibility for the deaths of innocent Americans,” said Mayor Stephanie Miner of Syracuse, New York.

“Failure to address an issue that amounts to slow-motion mass murder of American citizens, many of whom are black and brown, is political cowardice. Stand up! Do the right thing,” said Mayor Sly James of Kansas City, Missouri.

Chula Vista Mayor Mary Salas said she had a simple message for Congress: “Get a backbone—do your job.”

Those answers were part of an exclusive Politico Magazine survey, which also found that more than 90 percent of mayors say that Congress is doing too little on issues of firearm regulation and gun violence. As Tom Barrett, the mayor of Milwaukee, a city that has seen a surging homicide rate this year, implored: “Stand up against the fear-mongering NRA.” That emotion was seconded by Grand Rapids, Michigan, Mayor George Heartwell, who said, “Buck up and stand up to the NRA. Listen to the voice of the people of America.”

The mayor of Stamford, Connecticut, was even more blunt to Congress: “Just do it.”

The answers come from Politico Magazine’s third installment of an ongoing national Mayors’ Survey, part of the award-winning What Works series. The survey garnered responses from 45 mayors across the country, from Las Vegas to Tallahassee, Houston to San Francisco, Phoenix to Chattanooga, Grand Rapids to Portland, Maine. While not scientific (the large majority of respondents, 85 percent, were Democrats, joined by four independents and three Republicans), the survey represents an array of cities about as diverse as size, politics and geography can allow, including states of every hue—red, blue and purple.

Nearly across the board, the urban and suburban mayors—where the vast preponderance of the nation’s crime and gun violence occurs—were disturbed by rising homicide trends; 91 percent of the mayors said they were either “deeply concerned” or “concerned” about crime and homicide trends in their city. One in four of the mayors surveyed said their city had suffered a “mass shooting” incident since they came into office—and those mayors were substantially more likely to say they were “deeply concerned” about crime and shootings.

“We are losing an entire American generation to this endless cycle of violence,” said Mayor Mitch Landreiu of New Orleans. “It’s a direct threat to our national well-being and security.”

“The time to act is now,” Richmond, Virginia, Mayor Dwight Jones said. “We cannot wait to continue to allow illegals guns to subvert our neighborhoods and communities.”

Such fears now lie at the heart of an inflamed national debate over the proper role of government in regulating guns. Twenty years ago, it was the federal government that took the lead in creating such policy, passing landmark legislation such as the so-called Brady Bill and the federal Assault Weapons Ban of the 1990s. Cities followed suit, passing longstanding handgun bans like those in Washington, D.C., and Chicago. But a changing national mood—accompanied by the astonishing rise and power of groups like the National Rifle Association—have brought a new era of deregulation as the assault weapons ban expired, handgun bans were struck down by the Supreme Court and a raft of state legislatures passed controversial “open carry” and “stand your ground” laws. A simultaneous rise in the number and severity of mass shootings—Virginia Tech, Sandy Hook, Aurora and, most recently, Roseburg, Oregon—has become a rallying cry for new gun violence coalitions like Mayors Against Illegal Guns, largely underwritten by billionaire former New York City Mayor Michael Bloomberg.

Similarly, the mayors strongly backed President Barack Obama’s push for congressional action on gun control, believing that more gun regulation, rather than less, was the answer to the crime and shootings. They resoundingly opposed, by roughly a 9-1 margin, both “open carry” proposals and the idea of arming teachers or principals as a way to increase school security.

Washington inaction is one reason that more than 90 percent of the mayors surveyed said they believe cities and municipalities should be able to implement their own tougher gun restrictions than exist in their home states or by the federal government. They said that at the federal, state or local level, they overwhelmingly support a wide variety of gun control measures—include expanded/stricter background checks (90 percent); closing the so-called “gun show loophole” (86 percent); expanding gun-buying restrictions to prohibit people subject to restraining orders (78 percent); closing a federal loophole that allows gun sales to proceed unless the FBI background check is completed within three days (78 percent); renewing the federal assault weapons ban (80 percent); and stiffening penalties for “straw purchases” (73 percent).

“Congress should act to protect the vast majority of residents by enacting sensible gun control measures,” Long Beach, California, Mayor Robert Garcia said. “There is no question that easy access to guns makes all of us less safe.”

I attended a gun buy-back program hosted by the police at a local church,” wrote Mayor Megan Barry of Nashville, Tennessee, who later implored Congress to act. “Across the street, there were individuals standing on the sidewalk offering to purchase the guns before they were brought in.”

Just nine percent of the mayors surveyed said they supported no further gun control, with Tulsa, Oklahoma, Mayor Dewey Bartlett Jr. saying that he “[honors] the Constitutional right of a U.S. citizen to bear arms.”

More typical, though, were responses like that from Houston Mayor Annise Parker, who said she believes the Second Amendment clearly allows for some gun laws. As she put it, “‘A well ordered militia surely means that reasonable controls on who can buy and/or own a gun are constitutional. Local officials are the ones best able to determine when and where concealed handguns should be carried.”

Honolulu Mayor Kirk Caldwell said, “Hawaii has the lowest rate of gun deaths in the entire nation, for one simple reason: We have strict gun laws. I strongly support the rights of law abiding citizens to own guns, but no one in Hawaii gets a gun license without a strict background check at the police department. We also benefit from the fact that it’s impossible to drive an illegal gun here from another state.”

Absent a real commitment from Congress—which mayor after mayor said was clearly lacking—it’s no surprise that the residents of the nation’s cities were increasingly fearful of crime and shootings. As Dayton, Ohio, Mayor Nan Whaley said, “This country is doing nothing and then elected congressmen have the audacity to seem surprised when we have a now near weekly devastation in our cities and unnecessary loss of life. We should not be surprised by this ending because our legislators choose to take no action.”

Hartford, Connecticut, Mayor Pedro Segarra had an even simpler message for Congress: “Get to work.”

—Politico researcher Jesse Rifkin contributed reporting to this article.

SURVEY PARTICIPANTS (45): AC Wharton Jr., Memphis, TN; Andrew Gillum, Tallahassee, FL; Andy Berke, Chattanooga, TN; Annise Parker, Houston, TX; Anthony Silva, Stockton, CA; Bao Nguyen, Garden Grove, CA; Betsy Hodges, Minneapolis, MN; Carolyn G. Goodman, Las Vegas, NV; Davd Martin, Stamford, CT; Dennis P. Williams, Wilmington, DE; Dewey Bartlett Jr., Tulsa, OK; Don Lane, Santa Cruz, CA; Dwight C. Jones, Richmond, VA; Edwin Lee, San Francisco, CA; Elizabeth Tisdahl, Evanston, IL; Esther Manheimer, Asheville, NC; George Heartwell, Grand Rapids, Michigan; Greg Stanton, Phoenix, AZ; Hardie Davis, Augusta, GA; Helene Schneider, Santa Barbara, CA; Jack Seiler, Fort Lauderdale, FL; Jesse Molina, Moreno Valley, CA; Joseph M. Petty Worcester, MA; Kirk Caldwell, Honolulu, HI; Marni Sawicki, Cape Coral, FL; Mary Casillas Salas, Chula Vista, CA; Mayor Jorge Elorza, Providence, RI; Martin J. Walsh, Boston, MA; Mayor Osby Davis, Vallejo, CA; Mayor Robert Garcia, Long Beach, CA; Tom Barrett, Milwaukee, WI; Megan Barry, Nashville, TN; Michael F. Brennan, Portland, Maine; Mick Cornett, Oklahoma City; Mitch Landrieu, New Orleans, LA; Miro Weinberger, Burlington, VT; Nan Whaley, Dayton, OH; Noam Bramson, New Rochelle, NY; Paul Soglin, Madison, WI; Pedro Segarra, Hartford, CT; Robert Stephens, Springfield, MO; Stephanie A. Miner, Syracuse, NY; Sylvester "Sly" James, Jr., Kansas City, Missouri; Toni N. Harp, New Haven, CT; Tony T. Yarber, Jackson, MS.