AUGUSTA — Ten candidates — six Republicans and four Democrats — are now in the running to replace Olympia Snowe in the U.S. Senate.

All 10 qualified for the June 10 primaries by handing in nomination papers and voter signatures before the end of the day Thursday, according to the Secretary of State’s Office.

Most of the candidates are party leaders at the state level, and will now have to work fast to introduce themselves to voters.

Although Snowe’s surprise retirement had some of the biggest names in Maine politics toying with a run, none of the 10 primary candidates has held a national office or won a statewide election.

Their likely opponent in November has, however. Former Gov. Angus King has said he is in the race, but as an independent does not have to file his nomination papers until June 1.

The Republican primary is a six-way race that features several leaders in state government — including all three of Maine’s constitutional officers.

They are former Maine Senate President Rick Bennett, Assistant Senate Majority Leader Debra Plowman, State Treasurer Bruce Poliquin, Attorney General William Schneider and Secretary of State Charlie Summers. The final candidate, Scott D’Amboise of Lisbon Falls, is a conservative with tea party support and was the only one of the candidates to enter the race before Snowe’s announcement.

The Democratic primary also features candidates with experience at the State House, including former legislator and Secretary of State Matthew Dunlap of Orono, Sen. Cynthia Dill of Cape Elizabeth and Rep. Jon Hinck of Portland. Businessman Benjamin Pollard of Portland was the fourth candidate to qualify for the June 10 ballot.

Three big-name Democrats toyed with a run, but decided against it. They are former Gov. John Baldacci and Maine’s two U.S. House Representatives, Mike Michaud and Chellie Pingree.

Many predicted Snowe’s announcement would shake up all the statewide races this year. However, both Pingree and Michaud decided to stick to their original plans and run for re-election rather than seek Snowe’s seat.

Republican and Democratic party officials said Thursday the strong quality of their primary candidates gives them a real chance to win the open seat, one that could help determine the balance of power in the U.S. Senate.

Political scientists said the question is whether either party’s nominee can overcome King’s name recognition and favorable public image, however.

“The voters only are vaguely aware of (the Republican) candidates,” said Douglas Hodgkin, a retired Bates College political science professor who is active in the Republican party.

“You have basically second tier candidates in both the Democratic and Republican primaries,” said Sandy Maisel, a government professor at Colby College who was active in the Democratic party. “Maybe in the course of the campaign one of the candidates” will emerge as a challenger to King.

The Republican primary looks somewhat like the party’s gubernatorial primary in 2010.

In that race, seven candidates split the votes in unpredictable ways. Gov. Paul LePage, considered the most conservative candidate in the field, surprised observers by easily winning with 37 percent of the vote.

The three constitutional officers — Schneider, Summers and Poliquin — have the advantage of some name recognition outside the State House, Hodgkin said.

Poliquin, who also is believed to have the most personal money to finance the primary campaign, has earned respect among Republicans for his criticism of spending by the Maine State Housing Authority, he said. On the other hand, public questions about conflicts of interest with Poliquin’s private businesses and his use of a tree growth tax abatement will not help, he said. Poliquin also gathered only 4.9 percent of the vote in the 2010 gubernatorial primary, he said.

Two of the Republicans — Summers and Bennett — have the advantage of having run for Congress in the past.

“That may have some bearing on people’s recognition factor,” he said.

Plowman has the advantage of the only Republican woman in the race to replace Snowe.

D’Amboise also can’t be discounted, according to Hodgkin. A candidate could win with less than 30 percent of the vote, and D’Amboise — like LePage in 2010 — has support among Tea Party conservatives.

“He has strong commitment from activists on the ground,” Hodgkin said.

The Democratic side also is hard to predict, the political scientists said. What’s most striking about the democratic primary, they said, is that the dust has settled and the four candidates running now are the same ones who were running when Snowe was still in the race.

King’s entrance discouraged any better known candidates from jumping in, Maisel said.

“Governor King, in many ways, preempted the field,” he said. “It’s very difficult for a Democratic candidate to run against him with any kind of negative campaign.”

Snowe’s announcement that she would retire because of partisanship and dysfunction in the Senate is an ideal set-up for an anti-party candidate such as King.

In fact, Maisel now believes the Senate race that some predicted would be an expensive, high-stakes contest will now be “a yawner” in the fall.

“I can’t see either national party is going to invest heavily in this race,” Maisel said.

Hodgkin disagreed, at least as far as the Republicans go. The GOP sees King as leaning toward voting with Democrats, he said.

“The Republicans will not want to give up this seat,” Hodgkin said. “It will be a good race, unless both parties quite frankly take a dive and nominate someone who represents an extreme.”

Many of the candidates, meanwhile, issue statements this week saying they are in it to win and looking forward to the fall election.

Hinck, the Democrat, said one thing hasn’t changed since Snowe got out of the race and King got in.

“We’re still running against somebody who’s already been declared the winner,” Hinck said.