A small sample of the many players in May's primary races. Clockwise from left: Clay Aiken, Allyson Schwartz, David Perdue, Mitch McConnell, Monica Wehby, Matt Bevin, Thom Tillis, David Brannon.
Aiken, Brannon, Schwartz, Perdue, Bevin, McConnell, Wehby: AP, Tillis: CQ Roll Call/Getty

May Madness: Here are the primaries to follow

Updated

Tuesday kicks off a month of primaries around the country, with voters in North Carolina, Ohio and Indiana going to the polls. Nebraska and West Virginia hold primaries on May 13 followed by a whole slew of states on May 20: Georgia, Pennsylvania, Kentucky, Arkansas, Idaho and Oregon. Here are the races to watch, starting with the Republican Senate primary in North Carolina.  

North Carolina’s 2016 dress rehearsal

In North Carolina, GOP voters will pick a nominee to challenge Democratic Sen. Kay Hagan, who is considered one of the most vulnerable incumbents in the country.

The race is notable for its big name endorsements. Jeb Bush and Mitt Romney are backing frontrunner Thom Tillis, the state’s House speaker, while Senator Rand Paul is supporting libertarian firebrand Greg Brannon and Mike Huckabee is backing conservative pastor Mark Harris. Tillis has a big lead in the polls but needs to hit 40% to avoid a runoff.

UP, 5/3/14, 10:41 AM ET

Major test ahead for the Republican Party

Is the Tea Party revolt within the Republican Party as big and strong as it’s been for the last 2 elections? NBC’s Kasie Hunt and the Charlotte Observer’s Jim Morrill look at the pivotal 2014 state of North Carolina and the Republican primary between…

There are also some competitive House primaries to watch on Tuesday. On the Democratic side, former American Idol runner-up Clay Aiken is in a tough race against state Commerce Secretary Keith Crisco for the chance to run against incumbent Republican Rep. Renee Ellmers. On the Republican side, iconoclast Rep. Walter Jones, who favors a non-interventionist foreign policy and often votes against GOP leadership, is heading off a fierce primary challenge from Taylor Griffin, who is running as a more conventional foreign policy hawk.

Kentucky’s tea party Hail Mary

Minority Leader Mitch McConnell looks poised to easily fend off a challenge from businessman Matt Bevin, who is running for the GOP nomination with the backing of a variety of national tea party groups.

4/10/14, 9:59 AM ET

Matt Bevin: 'We're tired of these plastic people'

Republican Kentucky Senate candidate Matt Bevin, the tea party-supported businessman challening Mitch McConnell, proclaims that races like theirs are “a battle for the heart and soul of the entire electoral process.”

Bevin has struggled to gain traction and McConnell’s team has been merciless at finding and exploiting weaknesses. The race has also taken a serious turn for the weird. In March, Bevin was caught attending a pro-cockfighting rally. When caught, he claimed for weeks that it wasn’t a cockfighting rally at all – that is, until video surfaced of him at the event explicitly telling attendees that he supported legalizing the practice.

Oregon’s GOP tries to get on the map

Election observers have mostly ignored Oregon until recently, since the state’s liberal lean gives Democratic Sen. Jeff Merkley a strong advantage. But Republicans think that they might have a chance at an upset, especially if 2014 ends up being a wave election for the party akin to 2010.

Morning Joe, 4/25/14, 6:57 AM ET

Will Merkley lose his seat?

Politico’s John Harris talks about challenger Monica Wehby’s “brilliant” and “innovative” ad, getting attention in the GOP race against incumbent Sen. Jeff Merkley.

National Republicans are especially excited about one candidate, Monica Wehby, a pediatric neurosurgeon with centrist views on social issues. Her first major ad, which featured a passionate testimonial from a former patient, garnered widespread praise. Wehby needs to get through a competitive primary against state representative Jason Conger before she can take on Merkley.

Georgia’s free-for-all

Georgia’s GOP Senate primary is an intense battle among five plausible candidates, including three sitting House members, a former gubernatorial candidate, and a millionaire CEO. The winner will face a formidable opponent in all-but-certain Democratic nominee Michelle Nunn, whose father, Sam Nunn, is a popular former Georgia senator. Incumbent Republican Sen. Saxby Chambliss is not seeking re-election this year. 

All In with Chris Hayes, 10/15/13, 9:43 PM ET

Meet Rep. Paul Broun

Chris Hayes spotlights Rep. Paul Broun, a man who sits on the House Science Committee, yet called evolution and the Big Bang theory “lies straight from the pit of hell.”

Polls show a tight, evenly split race and it’s likely the top two candidates will face a runoff election in July. Businessman David Perdue has led a number of polls by narrow margins, but is still learning the ropes as a first-time campaigner and faces increased scrutiny of his corporate record. Rep. Jack Kingston got a recent boost from the Chamber of Commerce, and Secretary of State Karen Handel is touting an endorsement from Sarah Palin. National Republicans were nervous heading into the race that Rep. Paul Broun, a tea party favorite with a penchant for outrageous rhetoric, might make the runoff but his campaign has yet to take off. Rep. Phil Gingrey is less divisive but still might create some unique problems: he once said he partly agreed with Todd Akin’s infamous “legitimate rape” comments before apologizing.

Pennsylvania’s governor fight 

2014 is looking like a lousy year for Democrats for a bunch of reasons. But one bright spot is Pennsylvania, where they have a good chance of unseating embattled Republican Gov. Tom Corbett.

The Last Word with Lawrence O’Donnell, 4/21/14, 11:26 PM ET

Schwartz embraces Obamacare in campaign ad

In an exclusive, Rep. Allyson Schwartz unveils her new gubernatorial ad touting her role in getting the Affordable Care Act passed. She joins Ari Melber and Richard Wolffe.

Rep. Allyson Schwartz was widely thought to be the party’s top contender heading into the Democratic primary, but she and state treasurer Rob McCord are playing catch up in the polls with businessman Tom Wolf, who built a strong lead with a major early advertising campaign. As the race enters its heated final stretch, there are plenty of attack ads to go around. 

May Madness: Here are the primaries to follow

Updated