Kelly led with 50% of poll respondents, while Masters had 42% in a race including all candidates, according to the poll.
In a head-to-head race, Kelly is at 52% while Masters is at 45%, according to the poll.
Kelly leads in nearly every group except for men, where Masters has support from 50% of respondents.
In the governor's race Republican Kari Lake and Democrat Katie Hobbs are in a tight contest, with Hobbs at 49% while Lake is at 48%, making the race nearly tied, the poll said.
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More than 1,300 likely Arizona voters participated in the survey, conducted in mid-September by bipartisan polling team Fabrizio Ward & Impact Research.
The poll's margin of error is 4.4 percent for voters of all ages and 3.4 percent for voters 50 plus.
This article originally appeared on USA TODAY: Poll: Mark Kelly ahead of Republican Blake Masters in U.S. Senate race