WASHINGTON – Americans doubt Congress will enact new gun laws despite a spate of mass shootings this summer that rattled the country.

As lawmakers return to Washington, a nationwide USA TODAY/Suffolk University Poll found that less than a quarter of Americans think Congress will pass significant gun control legislation over the next year.

That’s despite the fact that the poll also found broad support for further controls over who can get a gun.

“Finally, a poll result that shows unanimity in the United States,” David Paleologos, director of the Suffolk University Political Research Center in Boston, said of the widespread support for universal background checks across every demographic including geography, gender, age, race and political party affiliation.

“If there ever was a time for lawmakers from both parties to act, it is now.”

The USA TODAY/Suffolk Poll of 1,000 registered voters by landline and cellphone Aug. 20-25 has a margin of error of plus or minus 3 percentage points.

It was conducted before the Aug. 31 shooting in Odessa, Texas, which prompted renewed calls from Democrats for the Senate to take up the bill for expanded background checks the House passed in February.

But a USA TODAY Network survey of all members of Congress in August found few Republicans willing to publicly back specific proposals on background checks or “red flag” laws, another proposal that was supported by a majority of Democratic and Republican voters alike in the poll.

Senate Majority Leader Mitch McConnell reiterated last week that he will bring to the floor only legislation that President Donald Trump has endorsed.

"If the president is in favor of a number of things that he has discussed openly and publicly, and I know that if we pass it it'll become law, I'll put it on the floor," the Kentucky Republican told conservative radio talk show host Hugh Hewitt.

Trump weighs in:'Congress has a lot of thinking to do' on gun control after Midland-Odessa shooting

Mixed messages from Trump

Since the August shootings, Trump has flipped between supporting enhanced background checks and warning of a “slippery slope” on gun control that could lead to infringements on gun owners' rights.

"If you look at background checks and if you look at some of – even the more severe and comprehensive ideas that are being put forward – it wouldn’t have stopped any of the last few years’ worth of these mass shootings, which is a problem," Trump said last week.

The USA TODAY/Suffolk Poll may shed light on why Republicans are not eager to get out front on the question.

Fewer than 4 in 10 Republican voters said they could vote for a candidate who disagreed with them on gun issues. That compares with just over half of Democrats and independents surveyed who said they could back a candidate with different views on gun control if they agreed with them on other policies.

Odessa shooting:Texas lawmaker's defiant defense of gun rights sparks debate

And while two-thirds of Democrats surveyed thought shootings would increase over the next year, less than 40% of Republicans did.

Lanae Erickson, senior vice president of Third Way, a center-left group that backs bipartisan gun control, calls support among Republicans for universal background checks "wide but not deep."

“It’s not a major priority for almost any Republican voter who supports it, and the minority who oppose it viciously hate the idea," she said. "That’s a strong incentive not to go out on a limb here, at least for the bulk of Republicans who can win with just their base."

House bill on background checks

The bill that passed the House in February with backing from eight Republicans would require background checks for all firearms sales and most transfers, including those at gun shows, online or in other private settings.

The House bill:The gun control legislation Mitch McConnell won't allow senators to vote on

The gunman who killed seven people in a rampage along a west Texas highway Aug. 31, who had failed a federal background check in 2014, got his AR-style rifle through a private sale, according to The Associated Press.

"The Senate must vote on the House bill next week – not a diluted bill, not a bill on other matters," Senate Minority Leader Charles Schumer, D-N.Y., said last week.

Nine out of 10 of registered voters surveyed in the USA TODAY/Suffolk Poll said they support requiring background checks for all firearm sales.

“All I can say is, I would like everyone who has a gun to have gone through a background check,” said Dianne Griswold, a retired teacher from Michigan.

Most Democratic members of Congress told the USA TODAY Network they support requiring background checks for all firearm sales, as well as federal incentives for states to pass “red flag” laws that allow courts to temporarily take firearms away from people suspected of being a danger to the public or to themselves. They also backed bans on the sale of some semi-automatic assault-style weapons and banning magazines that hold more than 10 rounds of ammunition.

Most Republican lawmakers declined to respond directly – or at all – when asked to give a yes or no answer to whether they support each of those measures.

That was true even for some Republicans, like Indiana Sen. Mike Braun, who has expressed an openness to some of the proposals.

But Braun did not want to be recorded as supporting or opposing requiring background checks for all firearm sales. He also declined to directly say if he supports federal incentives for red flag laws, which Indiana already has.

Instead, he offered the general statement that "watching Congress do nothing is unacceptable" and "any bipartisan legislation needs to include stronger background checks, red flag laws" and commonsense solutions.

Because of such statements, Braun has been targeted by the National Association for Gun Rights, which has warned its Indiana supporters that Braun is "running around Indiana – offering his support for dangerous `Red Flag' Gun Confiscation" and "wants to expand the Universal Brady Gun Registration Scheme!"

What about semi-automatic weapons?

Still, 85% of Republican voters said they support requiring background checks for all firearm sales. About half (52%) also said they support federal incentives for states to pass “red flag” laws – an idea backed by 69% of all poll respondents.

The House Judiciary Committee is scheduled to vote this week on legislation that would give federal money to states that pass red flag laws and on whether to ban high-capacity ammunition magazines. Lawmakers have scheduled a hearing for later in September on proposals to stop sales of some military-style assault weapons.

Pack bags only:Which stores besides Walmart, Kroger want you to leave guns at home

Before you shop:5 things to know about Walmart's stance on guns and open carry

Bans on some semi-automatic weapons and on high-capacity magazines were supported by about six out of 10 survey respondents, including by a majority of Democratic and independent voters.

“I don’t think that they should have the magazines. I don’t think they should have the assault rifles,” said Tomi Michaud, 50, a Democrat from Illinois.

But both of those proposals were backed by less than 40% of Republican voters.

“Personally, I think you should be able to own a Sherman tank if you want one,” said Steve Harold, 63, a mechanic from Illinois.

Only two Republican lawmakers told the USA TODAY Network they support bans on both high-capacity magazines and some semi-automatic weapons: Rep. Chris Smith of New Jersey and Rep. Peter King of New York.

“I voted in favor of the 1994 assault weapons ban and believe an assault weapons ban should be reinstated,” Smith said.

The more common response from Republican lawmakers was to focus not on the weapons used in the mass shootings but on the person pulling the trigger.

“The right approach to preventing mass shootings is not restricting the constitutional rights of law-abiding citizens,” Texas Sen. Ted Cruz told USA TODAY. “The right approach is to come down on criminals like a ton of bricks and prevent guns from falling into the wrong hands.”

While 54% of Democratic voters surveyed said the recent mass shootings have made them more likely to support gun control measures, half of Republicans and independents in the USA TODAY/Suffolk University Poll said the shootings haven't affected their views. And 23% of Republicans said the shootings have made them more likely to support gun owners' rights.

Perhaps reflecting that view, Rep. Ralph Abraham, R-La., said he hasn’t seen any proposals that would have prevented any of the shootings.

“I’m not in favor of doing something just to do something,” Abraham said, “and the Second Amendment is self-explanatory.”

Contributing: John Kelly and Jeanine Santucci of USA TODAY; reporters throughout the USA TODAY Network

USA TODAY/Suffolk poll:Americans dread the 2020 election