New poll numbers show U.S. Sen. Jeff Flake's approval rating is low, following his vote against expanding background checks for gun sales nationwide.

The proposal, which polling shows more than 70 percent of Arizonans support, failed in a Senate vote earlier this month after 46 Senators opposed it. Even though it got more than 50 votes, it didn't meet the 60-vote threshold required for passage.

Arizona's Flake voted against it, while Sen. John McCain voted for the bill. Sponsors have vowed to bring the proposal back for a second vote.

In polling numbers released Monday, Flake dropped to 32 percent approval rating, and 52 percent of Arizonans said that vote makes them less likely to support him in the future.

Just a few months into his first year as a senator, and "he’s actually already the most unpopular senator in the country," said Tom Jensen, director of Public Policy Polling, which conducted the surveys.

Voters said they trust McCain more than Flake following their respective background check votes.

It was the first survey of Flake's approval rating since his November election, and Jensen said he attributes the numbers to Flake's background check vote.

The support among Arizonans for expanding background checks for gun sales crosses party lines, Jensen said. Among Democrats, 92 percent said they support an expansion, while 71 percent of independents and 50 percent of Republicans said they support expanding background checks for gun sales.

The reaction shouldn't be surprising, said Geoffrey Garin, president of Hart Research Associates. Polling before the vote showed widespread support for expanded checks, he said. The senators whose approval ratings are dropping must have underestimated the issue, he said.

“I think what they thought is that this is an issue that didn’t matter to people, or that folks really wouldn’t be paying attention, or that once the vote was over the issue would be over and the public would move on to other things," Garin said.

Public Policy Poling is often cited as a Democratic polling firm, because it works for Democrats, but Jensen said his past polling is accurate. He said his polling ahead of the November presidential election accurately predicted how swing states would vote, and he accurately tracked all Senate races, including Arizona's.

"So we’ve shown that even though we’re a Democratic polling company, more than anything else we’re just trying to measure public opinion as accurately as possible,” he said.

There’s been more focus on Flake’s vote than other senators', Jensen said, because of his friendship with former U.S. Rep. Gabrielle Giffords. She formed a political action committee this year, which is focused on reducing gun violence.

Her committee ran ads in Arizona asking Flake to vote for the expanded checks, and after his vote, she and others have scrutinized Flake.

"I feel like that scrutiny maybe more so even for other senators, has really created the conditions for this vote to be a political liability for him," Jensen said.

The polling also shows the vote could have implications for the Republican push to attract Latino voters.

About 75 percent of Arizona Latinos polled said they support expanding background checks, Jensen said. Following his vote, 61 percent of Latino voters said they are less likely to vote for Flake in a future election.

The poll surveyed 600 Arizona voters and has a margin of error of 4 percent.