Democratic candidate Mark Kelly is leading Republican Sen. Martha McSally among Arizona voters, according to a new poll.

Kelly, a former astronaut and U.S. Navy captain, has a 4-point lead over the incumbent Republican, according to a poll by the left-leaning Public Policy Polling.

The survey found that 46 percent of polled voters said they would vote for Kelly and 42 percent said they would vote for McSally. An additional 12 percent said they were not sure.

Kelly is married to former Rep. Gabby Giffords (D-Ariz.) who has been a prominent a gun control advocate since retiring from Congress after surviving an assassination attempt in 2012.