King leads Maine Secretary of State Charlie Summers (R) by 50 to 24 percent, with state Sen. Cynthia Dill (D) at 12 percent, according to a new poll from the Pan Atlantic SMS Group. That's a contrast from a poll released late last month from the conservative Rasmussen Reports that had Summers within 12 points, and another from the Democratic Public Policy Polling that had him within 8 points.

The independent former governor's lead had slipped after a barrage of attack ads from outside groups including the Chamber of Commerce and the National Republican Senatorial Committee, but in the past week the Democratic Senatorial Campaign Committee and the Democratic outside group Majority PAC have both been spending heavily to drive down Summers's numbers, a sign they were concerned about the tightening race. New York Mayor Michael Bloomberg (I) will also host a fundraiser for King in a race few expected to be competitive when he jumped in.

The poll was conducted before Democrats began spending in earnest there, and it's unlikely King's lead was this large — otherwise, Democrats would not be spending to prop him up.

The live-caller poll of 400 likely voters was conducted from Sept. 24-28, including only respondents who voted in Maine’s 2010 gubernatorial election and are likely to vote again on Nov. 6 — an odd voter screen that may have impacted the result. Its margin of error is 4.9 percentage points.