WASHINGTON — Congressional Democrats are trying to build support for an effort to bar gun purchases by terror suspects, hoping to take advantage of the same public anxieties about security that gave Republicans a ringing House victory.

The Democratic push seems likely to be opposed by the National Rifle Association and congressional gun-rights backers, chiefly Republicans, who have smothered firearms curbs for years. If the Republicans who control Congress block votes on the proposal, Democrats hope to profit politically by winning sympathy from angry voters.

“By leaving this terrorist loophole open, Republicans are leaving every community in America vulnerable to attacks by terrorists armed with assault rifles and explosives purchased legally, in broad daylight,” Senate Minority Leader Harry Reid, D-Nev., said Friday.

The bill by Sen. Dianne Feinstein, D-Calif., would have the attorney general compile names of known and suspected terrorists, likely drawing from huge lists the government already keeps. Federally licensed gun dealers would be barred from selling firearms to people on that list if government officials believe they plan to use the weapons for terrorism.

Gun dealers are prohibited from selling to 10 categories of people, including many convicted criminals or those with severe mentally illness.

But people appearing on the government’s terror watch lists — including those kept off from airlines — are not automatically disqualified from buying weapons from gun dealers. The FBI is notified when a background check for the purchase of firearms or explosives generates a match with the watch list, and agents often use that information to step up surveillance on suspects.

Between 2004 and 2014, people on one terror watch list underwent background checks to buy guns 2,233 times and were allowed to make the purchase 91 percent of the time, according to a March report by the Government Accountability Office, an investigative agency of Congress.