The poll, published by Emerson College on Friday, found Masters with support from 48 percent of voters and Kelly with 47 percent. The poll surveyed 1,000 people and has a margin of error 3 percent.

The polling noted, however, that 1 percent of voters are undecided, and given the margin of error, the race is statistically tied.

Up until Friday’s poll, Masters had yet to surpass Kelly in public opinion surveys, though the two candidates had been tied in several polls. A poll released by InsiderAdvantage and Fox 10 this week found Kelly and Masters each with 48 percent. That poll had a margin of error of 4.2 percent and surveyed 550 likely voters.

However, another Friday poll, this time released by Marist College found Kelly up by 4 points, leading Masters 49 to 45 percent. The poll contacted over 1,200 voters and has a margin of error of just over 4 percent. In addition, Marist College pollsters noted that Masters previously had a 10-point lead in the race.

“Democratic candidates for Senate and Governor face strong headwinds in Arizona. They have an unpopular Democratic president, a Republican statewide electorate, and the economy as a top of mind issue for many voters,” Lee M. Miringoff, director of the Marist Institute for Public Opinion said in a statement, along with the latest poll results. “Right now, they are offsetting these disadvantages by carrying independents and attracting more Republican voters than their opponents are gaining among Democrats. This all adds up to two very close contests.”

The overall polling average in the race, compiled by FiveThirtyEight, shows Kelly with support from 48.1 percent of voters while Masters has the backing of 46.3 percent.

Meanwhile, a September poll by Emerson College found Kelly leading his Trump-backed Republican challenger 47 to 45 percent.

“Since September, Masters’ support has increased three points while Kelly has held 47%. A majority of voters (52%) expect Senator Mark Kelly to be re-elected, while 47% expect Masters to win,” Emerson College Polling wrote in a description of Friday’s survey.

Spencer Kimball, the executive director of Emerson College Polling, also said in the description that independents “break for Kelly over Masters, 50% to 42%.”

“Independent men break for Kelly by five points, 51% to 46%, whereas independent women break for Kelly by nine points, 48% to 37%,” he added.

Newsweek has reached out to the Kelly and Masters campaigns for comment.