Updated

Republican Charlie Summers and Democrat Cynthia Dill won their crowded primary elections, securing a spot on the November ballot along with former Gov. Angus King in the campaign for the seat that's being vacated by Republican U.S. Sen. Olympia Snowe.

The Republican and Democratic nominees will face the former two-term governor and several other independents in a race that could shift the balance of power in the Senate, where Democrats currently hold a 51-47 majority with two independents who caucus with them.

After her win Tuesday, Dill said the Democratic Party is ready for somebody who will stand up and be a strong voice in Washington for the middle class and small businesses.

"Democrats are ready to have a torchbearer who states very clearly and articulately what the Democratic core values are and not try to fudge and play to everyone in the political spectrum," she said.

Summers, meanwhile, said winning the general election will be a chore, but he thinks King's record as governor of increasing government spending and leaving his successor with a $1.5 billion deficit will be his downfall.

"Once Angus' record is out, it will speak for itself and I think we can be successful," Summers said.

All told, 10 Republicans and Democrats were on the ballot in Senate primary elections Tuesday after Snowe took the political establishment by surprise when she announced Feb. 28 that she wouldn't seek a fourth term.

Scott D'Amboise, who had intended to challenge Snowe in a primary, was soon joined by five other Republicans aiming for the spot. Big-name Democrats like U.S. Reps. Chellie Pingree and Mike Michaud and former Gov. John Baldacci considered joining the race but opted out, leaving Dill and three other Democrats.

D'Amboise, a small businessman from Lisbon Falls, was joined on the GOP ballot by Summers, the secretary of state from Scarborough; Poliquin, state treasurer from Georgetown; and Rick Bennett, a former Senate president and CEO of a corporate watchdog firm from Oxford, along with Attorney General William Schneider of Durham and Debra Plowman of Hampden, state senator and co-owner of a garage door business.

Democrats on the primary ballot were Dill, a state senator from Cape Elizabeth, and Matthew Dunlap, former secretary of state from Old Town, along with Rep. Jon Hinck of Portland and Ben Pollard, a Portland homebuilder.

Summers was leading with 30 percent of the vote followed by Poliquin with 23 percent, with 82 percent of the state's precincts reporting in unofficial returns early Wednesday in the GOP primary. In the Democratic primary, Dill had 45 percent to 35 percent for Dunlap.

King, who wasn't even on Tuesday's primary ballot, cast a long shadow on the campaign.

"For any of these candidates to knock him off is going to take a monumental effort," said Mark Brewer, political science professor at the University of Maine.

Republicans were all but assured of holding onto the seat before Snowe's departure.

In the primary campaign, the six Republicans hoping to be Snowe's successor focused much of their attention on King, a former Democrat, attacking him as a free-spending liberal and thinly disguised Democrat-in-independent's clothing.

Democrats battled to show they that can produce a candidate strong enough to take on the Republican nominee as well as King, a self-made millionaire.

Also on the ballot will be three other independents, including businessman Steve Woods of Yarmouth and tea party activist Andrew Ian Dodge.

Summers touted his resume. He's a former state lawmaker, small business owner, aide to Snowe and regional administrator of the Small Business Administration. As a Navy reservist, he spent time in both Iraq and Afghanistan "It proved I wasn't a one-dimensional candidate," he said.

Dill, for her part, has ascended from her local town council to the state House of Representatives to the state Senate. Along the way, she's taken shots from Republicans who have labeled her as an ultraliberal. She calls herself progressive.

She described King's candidacy as "some sort of political or social experiment" and said she looks forward to debating him on the issues.

On Tuesday, many voters said they viewed King as difficult to beat. And Democrats worried that the former member of their party could siphon off Democratic votes and give Republicans an advantage.

"The reality is that I do think Angus King will win the general election," said Elizabeth Simpson, a Democrat who voted for Dill Tuesday and said she'd vote for King if necessary in November to keep the Senate out of GOP hands.

Peter Gaulke, a left-leaning Republican, said he couldn't vote for any of the GOP candidates on the primary ballot so he wrote in King's name. "I'd just like to see people be more pragmatic. Ideology has gone too far," he said.