WASHINGTON — National Republican leaders will hold a fundraiser for Senate candidate Charlie Summers this evening in Washington, D.C., amid growing optimism that Maine’s Senate seat could remain within Republican ranks.

The National Republican Senatorial Committee and members of the Senate Republican leadership are hosting the fundraiser, which lists donation levels from $250 to $5,000.

Among the notables on the invitation are Senate Minority Leader Mitch McConnell of Kentucky, Republican Whip Sen. Jon Kyl of Arizona and National Republican Senatorial Committee Chairman Sen. John Cornyn of Texas.

Drew Brandewie, spokesman for the Summers campaign, said Wednesday he was unsure how many Senate leaders planned to attend but added that Cornyn is expected to be there.

The event follows an infusion of money into the race from out-of-state groups and several polls showing that front-runner Angus King’s lead is narrowing.

“Charlie’s message is resonating,” Brandewie said. “The race is tightening.”

U.S. Sen. Olympia Snowe is listed as a co-host on the invitation, but the retiring Maine Republican will not be in attendance. Maine Sen. Susan Collins planned to attend the fundraiser, staff said.

Snowe’s absence is notable, however.

Snowe had said before the primary won by Summers – a former staffer of hers – that she would support the Republican nominee, hence her willingness to allow her name to be used on fundraising invitations. But she has yet to campaign for him or donate money to Summers’ campaign.

“She wants to be supportive of the Republican ticket,” said Lucas Caron, spokesman for Snowe’s newly established political action committee, OLYMPIA’s List. “But her focus is not on political campaigning at this time.”

The two have apparently had a chilly relationship since Summers failed to endorse Snowe over a Tea Party-backed candidate in the months before Snowe decided to retire. She was widely expected to handily win the primary and general election.

Snowe’s Washington staff said the senator and her husband, former Gov. John McKernan, planned to attend a gala at the Blaine House in Augusta on Wednesday night. The event is honoring McKernan’s mother, Barbara McKernan, who spearheaded renovations of the Blaine House 25 years ago.

This will be at least the second DC fundraiser for Summers; King has also attended at least two fundraisers in Washington.

The Washington fundraisers underscore the delicate dance that many congressional candidates must perform as they campaign back home all the while courting out-of-state donors.

Paul Herrnson, author of the book “Congressional Elections: Campaigning at home and in Washington,” said that amounts to essentially two campaigns as candidates search for votes back home and hunt for resources elsewhere.

The challenge is especially acute for challengers from less well-to-do areas, he said.

“Candidates go where the money is,” said Herrnson, a professor and director of the Center for American Politics and Citizenship at the University of Maryland. “The importance of this campaign for resources really can’t be under-estimated because candidates need money to reach out to voters.”

Filings with the Federal Election commission show that the NRSC has spent just shy of $1 million on television ads in Maine targeting King, an independent with widespread name recognition after two terms as governor. The ads so far do not mention Summers.

Other outside organizations have also targeted King seemingly with the goal of boosting the Democratic nominee, Cynthia Dill. That strategy appears aimed at splitting the Democratic and independent vote between King and Dill, thereby giving Summers a better shot at winning with less than a majority of the vote.

Those ads appear to be working. King’s lead has shrunk considerably in several recent polls, raising the possibility that Maine’s closely watched Senate race could become competitive after all. While Dill continues to trail well behind King in third place, she has picked up additional support from members of her own party, according to polling data.