PHOENIX – Democratic challenger Mark Kelly’s lead over incumbent Arizona Sen. Martha McSally is up to double digits, according to new polling.

Kelly leads the first-term Republican 51%-38%, with 10% undecided, in the poll released Tuesday by Phoenix-based research firm OH Predictive Insights. (Totals don’t add up to 100% because of rounding.)

The survey of 600 likely Arizona voters was conducted May 9-11 and has a 4% margin of error.

Kelly’s support was unchanged from last month’s polling by OH Predictive Insights, but McSally’s slipped from 42% in April.

#OHPI #POLL: @SenMcSallyAZ continues to struggle against @CaptMarkKelly, now trailing the former astronaut by 13 points in the #AZSen #election pic.twitter.com/tro6zrkGVO

— OHPI (@OHPredictive) May 20, 2020

The state’s independent voters, who traditionally have leaned right, are lining up behind the first-time candidate, OH Predictive Insights chief pollster Mike Noble told KTAR News 92.3 FM on Wednesday.

“They’re supporting Mark Kelly over Martha McSally by a two-to-one margin,” Noble said of independents.

Kelly has been gaining significant traction in Maricopa County, home to 60% of the state’s likely voters and where Noble said the former astronaut led by 5 percentage points a year ago.

“Currently he has an 18-point advantage over McSally, so that’s a 13-point shift,” Noble said of the race in Maricopa County.

Noble said only one Republican has ever lost Maricopa County and won a statewide election in Arizona, former Superintendent of Public Instruction Diane Douglas in 2014.

However, Noble said McSally has time to close the gap before the November election.

Valley political analyst Stan Barnes told KTAR News’ Arizona Morning News on Wednesday he had reason to be skeptical about the actual size of McSally’s deficit.

“Nonetheless, she must, indeed, stay the course, because the election is six months away, and I think the poll that we’re talking about is influenced very heavily by a very good television ad campaign run by the Kelly campaign,” Barnes said.

Barnes said the incumbent should continue aligning herself with President Donald Trump, even though he trails Democratic challenger Joe Biden in Arizona polling.

Barnes said Trump and McSally will “live and die together” in Arizona.

“That same voter who is loyal to the president, who is going to turn out, is not going to reward Martha McSally for a strategic move of putting distance between her and president,” he said.

“They’re in the same boat.”

The race to fill the two years remaining on the late John McCain’s term has already set a state record in combined fundraising at about $49 million, according to the most recent Federal Elections Commission reports.

The national Democratic Party is targeting the seat, to which McSally was appointed by Gov. Doug Ducey in December 2018, as a key prize in its attempt to build a Senate majority.

Follow @kstonezone