Mark Kelly|Flickr Photo by Gage Skidmore Mark Kelly|Flickr Photo by Gage Skidmore

In about three months, Mark Kelly has increased his lead over Martha McSally by four points. 

A new poll from Phoenix-based firm OH Predictive Insights shows Democrat Mark Kelly is now leading Republican Sen. Martha McSally by seven points in the race for Arizona’s open U.S. Senate seat. 

The poll of 600 likely voters found that 49% chose Kelly, while 42% supported McSally and 8% were undecided. 

Kelly, a former Navy pilot and astronaut, has increased his lead since the firm last polled the public in December, when he was ahead 47-44. 

“The battle for control of the Senate Chamber may very well come down to historically ruby-red Arizona,” Mike Noble, OHPI’s chief of research and managing partner, said in a press release. 

The polling firm found that Kelly’s rise since December can partially be attributed to growing favorability among men ages 55 and older. Previously, Kelly trailed McSally in this demographic 39-51, but this time tied with her at 45%. 

Democrats stand united behind Kelly at 90%, while Republicans gave McSally more lukewarm approval at 83%. Kelly also received support from 7% of Republicans, while 6% of Democrats went for McSally. Overall, more Republicans said they were undecided (8%) than Democrats (4%). 

Additionally, Independents favored Kelly 58-29, with 13% undecided.

McSally did take the lead among one demographic – white, non-Hispanic voters, which is Arizona’s largest ethnicity group. She’s leading among this demographic by five points, 48-43.

The poll, conducted by cellphone and landline March 3-4, had a margin of error of plus or minus 4%.

The winner of the race will serve out the rest of former Sen. John McCain’s term. McCain died in August 2018 of brain cancer, and Gov. Doug Ducey appointed McSally to the seat at the beginning of 2019. McSally ran for the state’s other Senate seat in 2018 but lost to Democrat Kyrsten Sinema.