U.S. Sen. Susan Collins and her likely Democratic challenger, Troy Jackson, are in a close race, though Jackson may have a slight edge, according to a new poll.

In a general election matchup between the two, 49% of likely voters would pick Jackson while 46% said they would pick Collins. Five percent said they were undecided or would select another candidate, according to the poll released Tuesday from the University of New Hampshire Survey Center.

The poll was completed by 1,236 Maine residents between July 15 and July 20, and had a margin of error of +/- 2.8%.

Jackson, a former lawmaker and president of the Maine Senate, is expected to secure the Democratic nomination for the U.S. Senate race at a convention Saturday. His candidacy comes after Graham Platner, who won the Democratic primary in June, dropped out of the race earlier this month following an allegation of sexual assault, which he has denied.

The poll is the first public survey of the race since Jackson emerged as the front-runner in a crowd of Democratic candidates vying to replace Platner, who announced July 8 he would be dropping out. At one point, more than a dozen candidates were seeking to replace Platner, though all of Jackson’s top rivals dropped out this past weekend after he secured overwhelming support at county caucuses where delegates to the convention were picked.

The poll, which overlapped with the caucuses, also found Jackson to be voters’ clear favorite among the Democrats vying for the nomination. Fifty-one percent of Democrats surveyed who voted in the June primary said they wanted to see Jackson become the nominee, compared to 26% who said they preferred Nirav Shah and 11% who preferred Shenna Bellows.

The race with Collins will be one of the most closely watched and expensive Senate races in the country this fall, as Democrats see the five-time incumbent Republican as vulnerable, and are eyeing her seat as a key pickup opportunity in their quest to take control of the upper chamber.

According to the poll, a majority of Mainers (53%) rate Collins as good or very good at bringing federal dollars to Maine — something she has long touted as a key strength.

But Collins is also less popular than Jackson, with 35% of Mainers surveyed reporting a favorable opinion of her and 53% saying they have an unfavorable opinion. Thirty-seven percent of those surveyed reported a favorable opinion of Jackson while only 32% viewed him unfavorably. Fifteen percent said they didn’t know enough about Jackson to have an opinion, while less than 1% didn’t know enough about Collins to have an opinion.

The poll also surveyed Maine voters on the governor’s race, which features Democrat Hannah Pingree, Republican Bobby Charles and independent Rick Bennett. In that race, 49% of likely voters said they would support Pingree, 35% said they’d support Charles and 6% said they would vote for Bennett. One percent said they would vote for another candidate, and 8% were undecided.

The results mirror a June survey from the New York Times, Portland Press Herald and Siena University that found Pingree had the support of 50% of likely voters, compared to 36% for Charles and 8% for Bennett.