Here are the country's most and least popular senators

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Senate Majority Leader Mitch McConnell, the country's least popular senator.

Eleven of the 12 most vulnerable senators up for reelection in 2018 saw their approval ratings drop in 2017, according to a new Morning Consult poll.

Nine of these lawmakers are Democrats seeking reelection in states that President Donald Trump carried in 2016, many by double-digit margins.

Sen. Jon Tester, a Montana Democrat, saw his net approval rating fall by 18 points over the course of the year - the biggest drop of any vulnerable incumbent.

Senate Majority Leader Mitch McConnell, a Kentucky Republican, and former Democratic presidential candidate Bernie Sanders of Vermont held on to their positions as the least and most popular senators in the country, respectively. The pair held these titles throughout 2017.

The Morning Consult rankings are based on a survey of more than 250,000 registered voters between Oct. 1 and Dec. 31.

The five least and most popular senators are: