Cheat Sheet: Senate Primaries in Indiana, North Carolina, Ohio

Voters go to the polls Tuesday for primary contests in three states that will help set the stage for the November midterm elections. Below, we bring you up to speed on the situation on the ground in the Senate battles in Indiana, North Carolina and Ohio:

Indiana:

The action here is on the Republican side, where establishment pick Dan Coats is being challenged by a pair of candidates, state senator Marlin Stutzman and former Rep. John Hostettler.

Coats (pictured) is expected to win the race, but his margin of victory could be telling. He spent nearly two decades in Congress, and, since leaving Capitol Hill, has worked as a lobbyist for a variety of industries. In hopes of capitalizing on the anti-Washington sentiment sweeping the GOP base, Stutzman and Hostettler have cast Coats as an unrepentant creature of the beltway.

They have also hammered Coats for living in Virginia up until the start of his campaign. And while Coats is plenty conservative - he suggests the Obama administration is rapidly moving the country "toward a European Socialist style of government" - his challengers have attacked from the right.

Stutzman has managed to pick up a pair of high-profile endorsements, from Sen. Jim DeMint and David Keene of the American Conservative Union. Even if he and Hostettler fall short, a relatively strong showing by the challengers could rattle a GOP establishment concerned about losing control of its base.

There isn't much in the way of suspense for the Democrats: Sen. Evan Bayh's last-minute decision not to run for reelection meant the party isn't even holding a primary. Instead it has simply anointed its preferred candidate, Rep. Brad Ellsworth.

A former sheriff and centrist Democrat, Ellsworth is seen as a good choice for a state party left reeling by Bayh's surprise departure. But he will take heat for his support for the health care bill, and faces an uphill battle to get his name known across the state.

Expect a hard-fought battle to November: While President Obama won the state in 2008, Indiana has traditionally leaned red.

North Carolina:

It's a mess in the Tar Heel state, with a flurry of candidates battling for the Democratic Senate nomination. Among them: Secretary of State Elaine Marshall, Former State Sen. Cal Cunningham and Attorney Ken Lewis.

The front-runners are Marshall, the first woman elected to statewide office in North Carolina, and Cunningham, a former military prosecutor in Iraq who has the backing of the national Democratic establishment. If none of the Democrats manage to secure 40 percent of the vote - a not-unlikely scenario - there will be a runoff election on June 22nd.

That would be bad news for Democrats, who would prefer that their candidates stop spending time and money trying to take down each other and instead turn their guns on Sen. Richard Burr (pictured, at right), the overwhelmingly-likely GOP nominee. Burr won in 2004 with just 52 percent of the vote and currently has low favorability ratings; while he will likely still be the favorite in a general election, Democrats believe they have a chance to take the seat (and in doing so help limit the expected losses in the midterms).

Ohio:

With Republican Sen. George Voinovich retiring, Republicans have lined up behind former Congressman and George W. Bush budget director Rob Portman (pictured), who is running unopposed in the primary. Portman has taken advantage of his lack of competition and amassed nearly $8 million for use in the general election fight.

The Democratic side is far less orderly, with Lt. Gov Lee Fischer and Secretary of State Jennifer Brunner wrapping up a tough battle for the nomination. Fischer has a double-digit lead in polls and is expected to win, but don't look for Brunner to fall into line if he does: She has indicated she will not endorse Fischer or help him in the general election.

Both Democratic candidates have eaten into their financial resources in an effort to take each other out; Fischer has less than $1 million in the bank, and Brunner has virtually nothing. But if things look competitive in the general, as most expect, national Democrats will offer up cash to level the playing field.

CBS News Elections Director Anthony Salvanto contributed to this report.