PORTLAND — Angus King will go to New York City next week to get fundraising help from Mayor Michael Bloomberg, a fellow political independent who has already donated $500,000 to a group that hopes to propel King into the U.S. Senate.

Bloomberg will host King at his home in Manhattan Tuesday for an invitation-only fundraiser aimed at helping the former Maine governor raise campaign cash.

The trip and Bloomberg’s involvement is likely to intensify the debate over the influence of out-of-state interests funneling large sums into Maine in the national fight for control of the Senate.

“It’s just such hypocrisy,” said David Sorenson, spokesman for the Maine Republican Party.

The mayor’s name surfaced in connection with Maine’s Senate race last week, when Americans Elect, an organization that tried to create a bipartisan presidential ticket, acknowledged plans to spend more than $1.7 million on ads on King’s behalf.

Americans Elect is a nonprofit organization not affiliated with the King campaign, although Republicans have accused the two of illegal coordination. Bloomberg, the billionaire co-founder of the Bloomberg financial data-services company, contributed $500,000 of the $1.75 million donated so far.

Americans Elect stepped into the race at a critical time for King, who has been targeted for weeks with several million dollars’ worth of ads run by groups backing Republican candidate Charlie Summers.

“He believes (King) will bring the kind of independent, nonpartisan leadership that is sorely lacking in Washington today,” said Marc LaVorgna, a spokesman for Bloomberg at New York City Hall.

In an interview this week, King said he has met Bloomberg twice, first at an event in Oklahoma in 2006 that brought together prominent politicians who were independent or known for their bipartisan approach.

King said his second meeting with Bloomberg came in July at Bloomberg’s request after King’s well-publicized entrance into Maine’s Senate race.

Dan Janison, a political columnist with New York Newsday, said Bloomberg typically backs candidates he knows personally or who are viewed as sharing his “middle of the road” political views.

“He puts a lot (of emphasis) on personal relationships, and he likes to show himself to be an independent, anti-party kind of guy,” Janison said.

Bloomberg’s involvement in Maine’s Senate race generated national headlines last week. But King’s opposition in the Maine Republican Party has focused most of its scrutiny on Americans Elect, most notably on the past involvement of Eliot Cutler.

Cutler, a political independent who finished second in Maine’s 2010 gubernatorial election, served on the board of Americans Elect until the organization scrapped its 2012 presidential primary campaign. He is one of King’s campaign chairmen.

That prompted the Maine Republican Party to file a complaint with the Federal Election Commission, alleging illegal coordination between the King campaign and Americans Elect. Representatives from both organizations have dismissed the allegations as attempted distractions.

Americans Elect spokeswoman Ileana Wachtel released a copy of Cutler’s resignation letter showing he left in late June.

“Americans Elect did not conceive of or act on this effort to support the Angus King campaign until August 2012, and Eliot Cutler had nothing to do with this effort in any way,” Wachtel said.

Cutler isn’t the only connection between Americans Elect and King, however. The candidate worked with Peter Ackerman — co-founder of Americans Elect — on Unity08, a similar campaign to build a “unity ticket” for the 2008 presidential election.

Ackerman is one of the other two donors to American Elect’s independent expenditures supporting King. Federal Election Commission filings show that, like Bloomberg, he donated $500,000. John Burbank III, chief investment officer of the financial investment firm Passport Capital, donated $750,000.

Crystal Canney, spokeswoman for the King campaign, said the candidate has only met Ackerman three times and that they have never discussed Americans Elect. Similarly, Wachtel said the organization’s decision to support King was based solely on his vision and potential as an independent voice in Washington.

On Wednesday, the Maine Republican Party lodged a second official complaint, this time with the Internal Revenue Service challenging Americans Elect’s 501 nonprofit tax status. The complaint accuses Americans Elect of violating laws that prohibit nonprofit groups from engaging in political activity as their primary purpose.

“What this amounts to is taxpayer subsidy of the election of Angus King,” said Sorenson, the Maine GOP spokesman.

But Wachtel said that while Americans Elect is supporting King, the group’s primary activity remains attempting to open up the political process and ballot access to independent, nonpartisan candidates.

“We are not in violation of any rules,” she said.

Meanwhile, both Wachtel and King’s campaign have accused Maine Republicans of attempting to distract the public from the fact that Summers is trailing behind King in polls. Additionally, they pointed out that — unlike the U.S. Chamber of Commerce and other Republican-aligned running ads to help Summers — Bloomberg, Ackerman and Burbank all opted to make their contributions public.

“At least we know where the money is coming from,” Canney said. “We still don’t know where the money is coming from in the U.S. Chamber ads.”

Kevin Miller — 317-6256

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On Twitter: @KevinMillerDC