BANGOR, Me. -- The Maine Senate race has become so convoluted that at times it has seemed as if Karl Rove and Michael R. Bloomberg were running against each other.
Mr. Rove, the mastermind of Republican "super PAC" money, and Mr. Bloomberg, the billionaire mayor of New York, have injected considerable cash into this race (on opposing sides) and, as a result, have become proxies for their political allies. But that is not the only oddity here.
With an independent candidate as the perceived front-runner, a conservative Republican group actually paid for a series of television advertisements supporting the Democrat in the race, this after she was abandoned by her national party. And the Republican nominee has been cold-shouldered by Olympia J. Snowe, the popular Republican senator whose retirement led to the race to replace her.
Republicans were distraught when Ms. Snowe announced in February that she would not seek re-election. They had counted on her scoring an easy victory and helping the party take control of the Senate. Then Angus King, a popular former governor, entered the race as an independent, and he shot to the top of the polls.
Mr. King has refused to say which party he will side with if he wins, although many analysts expect him to vote with the Democrats, given his support for President Obama. So Republicans concluded that they at least had to try to knock off Mr. King if they wanted any chance of taking the Senate. Outside interests, notably Mr. Rove's Crossroads GPS and the U.S. Chamber of Commerce, joined the National Republican Senatorial Committee in pumping millions of dollars into television ads against Mr. King.
At the same time, the Democratic Senatorial Campaign Committee has kept its distance from its nominee, Cynthia Dill, a state senator, because they figured Mr. King had a better chance of winning than she did, and he would side with them anyway.
Now, after a tumultuous summer and fall in which party lines were scrambled and more than $6 million in outside money gushed into the state, Mr. King is still maintaining a double-digit lead in the polls.
This has discouraged some supporters of Charles Summers, the Republican nominee and Maine's secretary of state. Both the national Republican and Democratic Senate campaign committees have stopped buying TV ads in the state.
But Mr. Rove has not. Crossroads has just tossed another $335,000 into the pot for a new ad blasting Mr. King, saying he used his influence to help wind power companies like his own (a charge that the King campaign denies).
The last-minute infusion brings Crossroads' total spending in the race to nearly $1 million, and it has given some fresh hope to the Summers team.
"The fact that Crossroads has locked in for the final week with a new ad should reinforce the fact that this race continues to be seen as a winnable race for Charlie," Lance Dutson, Mr. Summers's campaign manager, wrote in an e-mail.
In the down-to-the-wire presidential contest, Mitt Romney has shown sudden interest in Maine; the state has been leaning toward Mr. Obama in the polls, but it awards its Electoral College votes based on results in the state's two Congressional Districts, and even one such vote could matter. Mr. Dutson said that television ad buys by the Romney camp "means a significant amount of resources will be spent to help get Charlie elected."
One of Mr. King's chief benefactors has been Mr. Bloomberg, who sent a $500,000 infusion as part of a $1.75 million donation from a group called Americans Elect. The group stepped in after the avalanche of negative ads started to hurt Mr. King. The mayor also started his own super PAC with plans to funnel up to $15 million more to various candidates, including Mr. King.
As the recipient of so much outside money himself, Mr. Summers has not complained too loudly about Mr. Bloomberg's involvement, except to cast Mr. King as a hypocrite. Mr. Summers has also sought to poke holes in Mr. King's notion that he can accomplish anything as an independent.
"We don't need an independent in the Senate," Mr. Summers said at a candidate's debate. "We don't need an umpire. Umpires don't win ballgames."
Mr. King's support eroded somewhat under an assault of ads that charged him with being a big spender and leaving the state with a deficit when he left office in 2003. But he never fell behind in the polls. One recently gave him an advantage of 26 percentage points; Real Clear Politics has him up over Mr. Summers by an average of 15 points.
One of Mr. Summers's problems is that he managed to alienate the moderate Ms. Snowe, his onetime political patron, who could have been a powerful ally. Before she decided not to seek re-election, he refused to endorse her when she was facing a Tea Party-backed challenger in a Republican primary; that cooled her interest in helping him as he sought to replace her.
Mark Brewer, a political scientist at the University of Maine, said that Mr. King had improved as a candidate, addressing concerns that he needed to be more specific in responding to criticisms about his tenure as governor and about what he wanted to accomplish in Washington.
But much of the campaign has revolved around the outside money, and Mr. King has sought to turn that to his advantage -- even though he, too, has been a recipient. "I feel, actually, like a walking economic development project," he joked here recently.
Maine, he said, has an opportunity to "make a statement to the negative-ad gurus and the political people that these ads don't work."
He said in an interview that using Mr. Rove's name had helped him with his own fund-raising because Mr. Rove was so well known and underscored that his race had national implications.
Whatever the outcome, it seems fair to say that traditional political parties in Maine, already somewhat off kilter with its Tea Party-backed governor, will be left in shambles after this campaign, particularly the Democratic Party. By cutting Ms. Dill loose, the national party gave local Democrats the cover to side with Mr. King. And just this week the conservative Safe Nation PAC spent nearly $25,000 on a pro-Dill mailing against Mr. King.
"The scariest thing for Democrats is that this will be their second nominee for a major race who will come in with under 20 percent of the vote in two years," said Jennifer Duffy, an analyst with the nonpartisan Cook Political Report. "They have a lot to worry about."
This article originally appeared in The New York Times.