The state of Arizona is a Republican state that has been (in fits and starts) trending Democratic starting with the 1992 Presidential election; since then, Democrats have been eyeing the state for potential flipping in Presidential years. While the state still voted for Donald Trump in last year’s Presidential elections, his 49-45% margin was a down tick from the 54-45% margin by which Mitt Romney carried the state in 2012.
The state’s junior Senator (Jeff Flake) similarly was narrowly elected in 2012 by a 49-46% margin (he actually ran BEHIND Mitt Romney that year), and he is up for re-election next year. However, he has a primary challenge from Kelli Ward, who held John McCain to a 51-40% win in the 2016 Senate primary. And in a late breaking development (after the poll was conducted), it looks like pardoned former Maricopa County Sheriff Joe Arpaio may be running as well.
JMC recently polled this primary race (the poll can be viewed here), and the poll shows that while the Arizona race is one of two races (Nevada is the other, which JMC also recently polled) that could determine partisan control of the U.S. Senate, Senator Flake has more immediate things to worry about, such as getting the Republicans to renominate him.