PORTLAND — Congressional hopefuls appeared on talk radio shows, met with voters on downtown streets and worked the phones Monday, a day ahead of the primaries to determine which party candidates will appear on November’s ballot.

Six Republicans and four Democrats are running in Tuesday’s primary election to determine which party candidates will move on to the general election to fill the U.S. Senate seat being vacated by Sen. Olympia Snowe. Two Republicans are seeking the GOP nomination in each of the two primaries in Maine’s two congressional districts, but there are no Democratic House primaries because U.S. Reps. Mike Michaud and Chellie Pingree are unopposed.

Based on the low number of requests for absentee ballots, state election officials are predicting a turnout of less than 20 percent of registered voters. But candidates in the Senate race say a large number of voters still haven’t made up their minds, leaving the outcomes up in the air.

“There are so many undecided voters. I don’t see how anyone can think they have an edge,” said state Sen. Debra Plowman, a Republican primary candidate who estimated that four in 10 voters are undecided based on her phone calls. “It means anyone can win in my book. We haven’t given up.”

Snowe’s surprise late-February announcement that she wouldn’t seek a fourth term initially created some buzz about the election and speculation about who might replace the Republican senator.

But former Gov. Angus King’s decision to enter the race as an independent has taken some of the life out of the Senate primaries. Many think it doesn’t matter who the GOP and the Democratic nominees are because King will win the general election regardless, Bill Vickerson, a Democrat, and Dave Stearns, a Republican, agreed while sitting in a Portland park at noontime Monday.

“But I think it probably means more to the Republicans than the Democrats because I think a lot of Democrats wouldn’t be unhappy with King,” said Vickerson, an attorney from Scarborough.

The candidates in the Republican Senate primary are Rick Bennett, CEO of a corporate watchdog firm; small businessman Scott D’Amboise; Plowman; state Treasurer Bruce Poliquin; Attorney General William Schneider; and Secretary of State Charlie Summers.

Running in the Democratic primary are state Sen. Cynthia Dill; former Secretary of State Matt Dunlap; state Rep. Jon Hinck; and home builder Benjamin Pollard.

In the Republican House primaries, state Sen. Jon Courtney faces merchant mariner Patrick Calder in the 1st district, and Senate President Kevin Raye faces Navy veteran and building contractor Blaine Richardson in the 2nd District.

The candidates spent Monday employing different last-minute campaign tactics.

Summers stopped at coffee shops and diners in Cumberland and York counties, while Bennett stopped at businesses and met residents in walks through downtowns in central and southern Maine.

D’Amboise also walked downtown districts in central Maine and planned to wave campaign signs with supporters during the afternoon rush hour in Topsham.

Plowman campaigned in the Bangor area and sent email and Facebook messages to supporters. Poliquin worked with volunteers in Damariscotta making phone calls to solicit support. Schneider worked in the attorney general’s office, but had a busy primary day planned.

On the Democratic side, candidates worked the phones and met with supporters Monday.

It’s been a relatively low-profile campaign, although some of the candidates have taken shots at each other.

Bennett and D’Amboise have criticized Poliquin, arguing he’s not the conservative he claims to be based on past contributions to a Democratic gubernatorial candidate, to a handgun control group and to a leading environmental advocacy group. Bennett has also taken aim at Summers, claiming Summers voted in favor of increased sales and gasoline taxes while in the Legislature in the early 1990s.

The primaries are a pivotal first step toward determining who will replace Snowe as Maine enters a new political era of representation in Washington, said Stearns, a business owner who lives in Kennebunk.

“This is a critical election,” he said. “I think this primary is important to see who’ll face Angus King.”

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