Here’s a state-by-state rundown of today’s competitive primaries and runoffs in six states.

MAINE

Senate

Sen. Olympia Snowe’s (R) late retirement announcement created an abridged and chaotic primary on the GOP side.

Former state Senate President Rick Bennett, state Treasurer Bruce Poliquin and Maine Secretary of State Charlie Summers are the top-tier candidates. Poliquin might have the edge because he has been on television and was able to self-fund the campaign while his opponents have lagged in fundraising.

On the Democratic side, state Sen. Cynthia Dill has courted the progressive vote as former Maine Secretary of State Matt Dunlap has focused on the mostly rural, northern 2nd district.

Turnout is expected to be light today, adding to the unpredictably of both contests.

Both candidates who emerge as the party nominees will begin the general election as underdogs.

Former Gov. Angus King is running as an Independent and is currently favored to succeed Snowe.

VIRGINIA

Senate

George Allen, the former governor and Senator, is expected to win the Republican primary against three lesser-known opponents: tea party leader Jamie Radtke, state Del. Bob Marshall and minister E.W. Jackson. The question is what percentage Allen will get. His campaign launched a two-week tour of the state, which included Virginia’s top GOP surrogates, to increase voter turnout and “send a message” to former Gov. Tim Kaine (D), his general election opponent.

Anything below 60 percent could be spun by the Kaine campaign as a GOP base unenthusiastic about another Allen term in the Senate. But in reality, the Kaine-Allen race is expected to be a hotly contested tossup through Election Day, regardless of today’s results.

NEVADA

4th district

Polls open: 7 p.m. to 7 p.m. PST

Republicans are holding out hope they can beat state Senate Majority Leader Steven Horsford (D) in November in this new district, despite its Democratic tilt. Nine candidates are running in the GOP primary today.

With no other major race on the ballot and turnout projected to be low, it’s difficult to handicap the race. 2010 Senate candidate Danny Tarkanian, state Sen. Barbara Cegavske and wealthy businessman Dan Schwartz, who’s been on TV the most, are the favorites and are all in the National Republican Congressional Committee’s Young Guns program.

SOUTH CAROLINA

7th district

Polls open: 7 a.m. to 7 p.m. EDT

Republicans expect colorful former Lt. Gov. André Bauer and Horry County Council Chairman Tom Rice to come out on top in today’s crowded GOP primary in the new Myrtle Beach-based 7th district. Other serious contenders include attorney Jay Jordan and Chad Prosser, former director of the state’s Department of Parks, Recreation and Tourism. No candidate is expected to get more than 50 percent of the vote, likely forcing the top two finishers into a June 26 runoff.

In the Democratic primary, the establishment shifted its support to attorney Preston Brittain after the frontrunner dropped out. But he faces a serious challenge from Gloria Bromell Tinubu, a former Georgia state Representative.

Republicans are favored to win the seat this fall.

NORTH DAKOTA

At-Large

Polls open: 7 a.m. to 8 p.m. CDT

Republicans could witness a historic upset in the open-seat at-large House race today. In the past month, two polls showed Public Service Commissioner Kevin Cramer (R) ahead of fellow Public Service Commissioner Brian Kalk, the state GOP’s backed candidate.

The latest survey — a new Mason-Dixon poll out over the weekend — showed Cramer ahead of Kalk, 60 percent to 21 percent, with 19 percent undecided.

North Dakota rarely hosts a competitive Congressional primary because the party traditionally coalesces behind its endorsed candidate at the state convention. But Cramer ran outside the convention process for the seat.

After Republicans backed Kalk in April, conservative groups got behind Cramer, setting the stage for an upset. The Club for Growth spent $63,000 boosting Cramer, while the Life and Marriage Political Action Committee spent $15,000 and FreedomWorks spent $7,500 supporting him, according to online fundraising reports.

“It was a calculated risk for Kevin Cramer to skip the convention, being a former state party executive director and chairman,” said Patrick Davis, a GOP consultant who works for Life and Marriage PAC. “It seems to have paid off.”

The winner of the GOP primary will face former state Rep. Pam Gulleson, the expected Democratic nominee, in November.

ARKANSAS

1st and 4th district runoffs

Polls open: 7:30 a.m. to 7:30 p.m. CDT

Democrats in the 1st and 4th districts will choose their nominee for Congress in a runoff today. In the 1st, either local prosecuting attorney Scott Ellington or state Rep. Clark Hall will take on Rep. Rick Crawford (R). Hall has establishment support, but it didn’t help him during the primary, which Ellington almost won outright. Crawford is favored to hold the seat in November.

In the 4th, either attorney Q. Byrum Hurst or state Sen. Gene Jeffress will have the unenviable task of taking on GOP nominee Tom Cotton, who is a very strong candidate and is seen as a rising star. Democrats are not favored to hold the seat of retiring Rep. Mike Ross (D) this fall.

— Kyle Trygstad, Abby Livingston, Joshua Miller and Shira Toeplitz