WASHINGTON (CNN) Democrats hold an advantage in two states that are critical to the party's chances of taking control of the US Senate, according to new CNN polls conducted by SSRS. The surveys show Democratic Rep. Kyrsten Sinema and former Gov. Phil Bredesen leading their Republican opponents for open seats Arizona and Tennessee, where sitting Republican senators are retiring.

In Arizona , Sinema tops Republican Rep. Martha McSally by 7 points, 50% to 43% among likely voters, while in Tennessee , Bredesen holds a 5-point edge over Rep. Marsha Blackburn, 50% to 45% among likely voters there. Roughly 1 in 6 voters in each state say there's a chance they'll change their mind before Election Day.

Likely voters are a subset of registered voters in the poll and include those most likely to turn out based on a combination of self-reported intention to vote, interest in the election and past voting behavior.

Arizona and Tennessee are two of the four states where Democrats are widely seen as having at least some chance of picking up Senate seats in November's election. The others are Texas -- viewed as more of a long-shot - and Nevada -- generally viewed as the Democrats' best chance for a Senate pickup. In order for the party to have any shot at taking control of the senate, it's almost certain that at least one seat from Arizona or Tennessee would need to go Democrats' way.

Arizona has been a Democratic target for some time on account of its changing demographic profile, though the state hasn't voted for a Democrat in major statewide elections since Janet Napolitano's turn as governor in the Bush years. Tennessee has generally moved away from its more Democratic-friendly past. Those differences are readily apparent in the two states' impressions of President Donald Trump in the new polls. In Tennessee, likely voters are about evenly split on the president's performance, 49% approve and 48% disapprove, far outpacing his nationwide approval rating in the latest CNN polling of 36%. In Arizona, by contrast, Trump fares only slightly better than his national number, with 39% of likely voters saying they approve of the way he's handling his job while 57% disapprove.

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