TUCSON, Ariz. (CN) – Former Vice President Joe Biden is the only top Democratic presidential candidate who would beat President Donald Trump in Arizona if the 2020 election were held today – and Biden’s lead has shrunk since May, a new poll of likely voters shows.

Biden would edge out Trump 45% to 43%, while Trump would beat Massachusetts Senator Elizabeth Warren 44% to 43%. Warren is the only other Democrat to poll within the margin of error. That’s a slight gain for Warren from a similar poll in May, but Biden’s lead dipped 3 points since then when he led Trump 49% to 44%, OH Predictive Insights chief researcher Mike Noble said in a statement.

“The biggest red flag is that Trump doesn’t cross the 50% threshold in any of these hypothetical matchups and is hovering in the low-to-mid forties,” Noble said. “The data continues to indicate that Arizona will likely be a battleground state in the upcoming 2020 presidential election.”

Trump would beat Vermont Senator Bernie Sanders in the Copper State, 44% to 34%. The president also would win today against South Bend, Indiana, mayor Pete Buttigieg (43% to 38%) and California Senator Kamala Harris (45% to 36%), the poll shows.

The poll also linked the 2020 election to gun control, asking whether voters would be more or less likely to vote for a candidate who backs “gun safety legislation.”

Not surprisingly, 79% of Arizona Democrats said they are more likely to vote for candidates who support those laws, while just 32% of Republicans did. Overall, 56% of Arizona voters said they would be more likely to back such candidates, with 19% less likely.

Arizonans are generally more likely to vote for candidates who back a “public option for Medicare.” Among Democrats, 67% told OH Predictive they would back those candidates, while 24% of Republicans did, and 13% declined to answer.

Climate change showed a stark split along party lines.

While 74% of Democrats said they would be more likely to vote for candidates who back “a climate change plan like the Green New Deal,” just 15% of Republicans did. Overall, 42% said they would be more likely to vote for candidates backing sweeping climate change legislation.

The number of Arizona voters who approve of Trump’s job performance dipped from 49% to 47% since May, while his disapproval rating rose from 50% to 52%, according to OH. Those numbers reflect more support for the president than a national poll published yesterday by SSRS, a research firm that partners with CNN.

That poll showed 40% of Americans think the president is doing a good job, while 54% told SSRS he isn’t.

“To win Arizona, Trump is going to have to do a better job of convincing voters he is the right man to lead on the economy and world affairs,” Noble said.