In what could prove to be a significant gain for Democrats in the U.S. Senate, a new poll shows former astronaut Mark Kelly now leading incumbent Sen. Martha McSally (R-AZ).

The poll, by Phoenix-based OH Predictive Insights has Kelly ahead of McSally 46% to 41%, reports The Hill. It’s the first time Kelly has led their race.

McSally has fallen behind … as President Trump’s standing takes a hit in Arizona,” says The Hill, quoting Republican pollster Mike Noble of OH Predictive Insights.

A possibly more worrisome trend for McSally is taking place in Maricopa County [Phoenix], “home to about 3 in 5 Arizona voters,” where she trails Kelly by 9 percentage points.

McSally, a former fighter pilot and member of the House, was appointed to the Senate seat of the late John McCain last December.

According to the OH poll, Kelly leads virtually every key demographic group: men, women, white voters — and by 18 points among Hispanics.

Kelly is married to former Representative Gabrielle Giffords.