Maine state House Speaker Sara Gideon (D) is leading Sen. Susan Collins Susan Margaret CollinsThe Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally Gideon leads Collins by 12 points in Maine Senate race: poll Senate leaders quash talk of rank-and-file COVID-19 deal MORE (R), in the race for Collins's U.S. Senate seat, according to a new poll.

Gideon has a 4-point lead in support from Mainers over the Republican incumbent, according to a poll released Thursday by the left-leaning Public Policy Polling.

Gideon has 47 percent support, compared with Collins’s 43 percent, based on the poll. The other 10 percent said they’re not sure who they would vote for between the two candidates in the fall.

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Gideon has made major gains on Collins since launching her campaign. A Public Policy Polling survey conducted last spring found Collins with an 18-point lead, at 51 percent compared with Gideon’s 33 percent, according to the polling firm.

Collins has been on thin ice with Maine voters, first catching blowback when she voted to confirm Supreme Court Justice Brett Kavanaugh Brett Michael KavanaughGideon leads Collins by 12 points in Maine Senate race: poll Conservatives see glaring omission on Trump's Supreme Court shortlist Cruz says he wouldn't accept Supreme Court nomination MORE after he was accused of sexual assault.

The criticism continued against Collins as she has voted with the majority of her party to acquit President Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE on impeachment charges. These decisions could cost her votes in November.

The March survey found nearly half of Mainers, 47 percent, said Collins voted to acquit Trump more so to vote with her party to protect Trump politically. Forty-three percent said Collins voted to acquit Trump more because she thought the president didn’t commit any impeachable offenses, based on the poll.

The Cook Political Report ranks the race as a toss-up.

Public Policy Polling surveyed 872 Maine voters between March 2 and 3. The margin of error is 3.3 percentage points.