2018’s first quarter was a volatile one for several senators, with lawmakers on both sides of the aisle seeing significant changes in levels of support from their constituents, according to the latest Morning Consult Senator Approval Rankings.

In the quarterly rankings — based on surveys conducted online with more than 275,000 registered voters nationwide from Jan. 1 through March 31 — a dozen senators saw their net approval ratings fluctuate by at least 9 percentage points from the previous three-month period. By comparison, two senators saw swings of that magnitude during the fourth quarter of 2017. See our methodology here.

Four senators posted net increases of 10 points or greater last quarter. Vulnerable Sen. Jon Tester (D-Mont.) led the way with a 16 point increase, vaulting him from the bottom 10 to the top 10. Fifty-six percent of Montanans approve of Tester, compared with one-third who don’t.

Sen. Bob Menendez (D-N.J.) also climbed out of the bottom 10 after a 12 point increase from the previous quarter. The Justice Department announced Jan. 31 that it was dropping its corruption case against the two-term incumbent, who’s up for re-election this year. Menendez had been a member of the bottom 10 for the previous three quarters.