 -- Last week, Maine voters chose the Democratic and Republican nominees for the open U.S. Senate seat, but Independent former Gov. Angus King continues to rule the race, according to a new poll.

King, who served as governor from 1995 to 2003, leads among likely voters with 50 percent support, according to a new MassINC poll commissioned by Boston NPR affiliate WBUR . Republican nominee Charlie Summers, the Maine Secretary of State, received 23 percent and Democratic nominee Cynthia Dill, a state senator, received 9 percent. The poll, conducted June 13-14, has a margin of error of plus or minus 4.4 percentage points.

Steven Koczela, the president of the MassINC explained in a radio interview Monday morning, that King begins the race with a lead simply because of his past experience. "He has considerably higher name recognition than his opponents," Koczela said on WBUR's Morning Edition. Koczela added that the poll found King's favorability rating to be 60 percent. Just 5 percent of respondents said they had never heard of King, compared to 23 percent for Summers and 35 percent for Dill.

Most of King's support stems from Democratic and Independent voters, said Koczela.

King has yet to explicitly state with which party he will caucus, but King and the national parties along with conventional wisdom suggest a Democratic pairing is much more likely than a Republican one. Republicans are attempting to use the awkward situation of the Democratic party attached to Dill but supporting King, as a way to castigate the party for abandoning Dill's campaign.

The National Republican Senatorial Committee has been hammering Democratic Senatorial Campaign Committee chairwoman Patty Murray for not endorsing Dill outright following his primary win last week.

Candidates are competing to succeed Republican Sen. Olympia Snowe, whose surprise retirement announcement this February turned this race into a major headache for the Republican party. Snowe won wide support from state voters for being a moderate and often refused to tow the Republican party line. Snowe cited partisanship as one reason why she has decided to retire.