PORTLAND — Former Gov. Angus King held a decisive lead in a poll released Wednesday morning, seeing twice the support of his closest challenger in Maine's U.S. Senate race.

Pan Atlantic SMS Group's Omnibus Poll found 50.3 percent of respondents likely to vote for or leaning toward King, an Independent, compared to 23.8 percent for Republican Charlie Summers and 12.1 percent for Democrat Cynthia Dill.

Another 13.8 percent were undecided.

All three are vying to fill the seat being vacated by U.S. Sen. Olympia Snowe.

Pan Atlantic conducted the telephone poll of 400 likely Maine voters between Sept. 24 and Sept. 28. It has a 4.9 percent margin of error.

In other results, if the presidential election was held tomorrow, 50.8 percent of respondents said they were likely to vote for or leaning toward President Barack Obama and 36.8 percent for Republican challenger Mitt Romney.

Ten percent were undecided.

Obama led in the poll with Independents: 49.6 percent said they were leaning toward the president, with 33.6 percent choosing Romney.

In Maine's first congressional district, the poll found support for incumbent Democrat Chellie Pingree at 56.5 percent versus Republican challenger Jonathan Courtney at 24.2 percent.

In the second congressional district, 52 percent of respondents said they were likely to vote for or leaning toward incumbent Democrat Mike Michaud. Republican challenger Kevin Raye was at 32.2 percent.