As promised, welcome to a Tuesday morning look at the biggest primary day of the year, so far. We'll probably be saying this on June 8, which is the day after President Obama gives a commencement speech at Kalamazoo High School in Michigan.

No, Michigan's primary is not that today, nor is it today.

It is tough to find a real "headliner" for today, with three races really meriting a ton of attention. That said, let's go to Pennsylvania, where a one-time Republican is running at a dead heat in the Democratic primary.

Last year, when then 79-year old Senator Arlen Specter decided to make the switch from Republican to Democrat, his motives were plainly clear: re-election. Democratic party identification continues to rise in Pennsylvania, a state Obama won by about 600,000 votes in 2008. However, as The Fix points out, blacks could decide this race.

Specter, who as a Republican in his 2004 re-election race won just 25 percent of black voters in a blow out win, is leaning heavily on President Obama, Gov. Ed Rendell, a former Philadelphia mayor and current Philadelphia Mayor Michael Nutter, who is black, to serve as surrogates to this critical voting bloc.

Why does the black vote matter? Specter, who is being opposed by 7th district representative Joe Sestak, cannot win this race without pulling off a large margin in Philadelphia. He may not need (nor will he receive) the 90 percent of black voters Obama won, but the 79 percent Governor Ed Rendell won in the Philadelphia media market in 2002 would clinch it.

One thing not to forget about this race is that Spector is shooting for his sixth term, while Sestak, despite being in the race for quite some time, is still relatively unknown. What we do know is that Sestak wants voters to be reminded of just who Arlen Specter has been his whole life.

What I will say about Specter, he hasn't taken his party switch lightly. He has voted for Democratic bills. And when the president was trying to get the stimulus package passed, Specter didn't hold out for pork. He held out for increased funding for cancer research.

This race is the most likely to have ramifications in Washington, as the White House, as well as pretty much the entire establishment, is backing Specter. A loss, not all that unlikely, could really sting. My biggest wonder is whether a guy like Specter, seemingly prideful, would change how he votes based on the loss.

Both candidates are running behind the Republican leader, Pat Toomey.

Another big race in Pennsylvania today, with some ties to one of our own. Washington state Representative Norm Dicks ascended to the chairmanship of the Defense Appropriations Subcommittee as a result of the death of John Murtha, who represented Pennsylvania's 12th district.

So, instead of a primary today, this is a special election, meaning this one will actually put someone in a seat when the results are tallied. And it's going to be close. Nearly $2 million has been spent by the national campaign arms of both parties, in an effort to elect one of Republican Tim Burns or Democrat Mark Critz. Burns has been up in the polls for quite some time, though I did see one with Critz up six points not long ago.

House dems are rolling on a two year streak in special elections, having won every one since May '08. The telling statistic: Dems out number the GOP 2-1 in the district. In other words, if they show up and vote, they win. If not, per usual, that is a GOP pickup.

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Off to Arkansas, where Republican Democrat Blanche Lincoln is trying to fend off a primary challenge from Lt. Gov. Bill Halter. While she has White House support, reluctantly, Lincoln has been getting hammered by labor unions and environmental groups. My former employer, LCV, has been letting her have it for months now.

The kicker in Arkansas (where it is illegal to pronounce it "ar-KAN-sas") is that candidates need to win 50 percent of the vote, or else there is a run-off. With Lincoln leading Halter in the 46-36 range, 11 percent undecided and six percent to a really conservative Dem, the latter looks likely. Obviously, given the undecideds involved, that is a negative for the incumbent.

Five Thirty Eight, one of the leading election blogs, has a good breakdown just how we got here in Bill Clinton's home state:

The polling in this race has consistently shown Lincoln to be in deep trouble in the general election and some peril in the primary after Halter jumped in on March 1. The latest poll, from DKos/R2K, has her down 54/40 against Boozman (and with a 39/55 favorable/unfavorable ratio); in early May Mason-Dixon had her trailing him 52/35; and a late April Rasmussen survey showed Lincoln down 28 points (57/29). Indeed, the sense that she was getting a little toasty had as much to do as ideology with Halter's entry into the race.

While the major ideological issue in the primary has been Lincoln's regular defections from Democratic Party orthodoxy--most notably her flip-flopping into opposition to the Employee Free Choice Act (which enraged labor) her less than helpful behavior on health reform, and her championship of large agribusiness interests--a late twist in the race has been her sponsorship of a very tough derivatives regulation provision in the financial reform bill currently before the Senate. Some have speculated that the Senate Democratic leadership is holding off a vote on Lincoln's provision until after the primary, when they intend to kill it.

Just how much has she rejected the Democratic party? Take a look at her main campaign ad, released in March:

Soon all she may be doing is answering the phone at home, unemployed.

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Those first two races were basically expected. This one in Kentucky, however, is the first real test of a divide between Republicans and the Tea Party. Jim Bunning, a baseball Hall of Famer and two-term senator, is mercifully retiring at the end of this term. Bunning, some may recall, quite famously blocked an extension in unemployment benefits earlier this year, telling another member "tough s***" and also complaining that his own tactic took so long that he had to miss a Kentucky basketball game. For a minute there I thought Bunning's block lasted longer than John Calipari's Kentucky coaching career. The old guy is quite literally off his rocker.

Anyway, running for his seat are Secretary of State Tray Grayson and a name you might recognize, Rand Paul. Yes, he is the son of Texas Representative, and former presidential, uh, candidate, Ron Paul. As you have probably surmised from such information, Paul is the Tea Party guy. And in Kentucky, the tea has been flowing.

It is widely expected that Paul will win this race tonight, right in the face of the state's senior senator, Minority Leader Mitch McConnell, who endorsed Grayson. Bunning backed Paul. All four men involved here are Republicans. They even cause division in their own party.

The real question about this one is what happens when Paul wins. For that, let me quote someone smarter than me. Cue, Chris Cillizza:

McConnell's rhetoric glosses over the real differences between the forces behind Paul and those who, like McConell, are supporting Grayson. The tea party movement has, to date, resisted any attempt by the party establishment to co-opt its power -- much less take over the campaign of one of its own.

Having won largely by running against Washington (and Republicans in Washington), how does Paul reconcile his past statements against the establishment with a party that knows it must rally around him? Will Paul, who has run a campaign light on consultants, bring on polling and media advisers recommended to him by the National Republican Senatorial Committee? If not, how do national Republicans handle Paul -- someone who, by definition, doesn't like to be handled by the powers-that-be?

I don't like to be handled either. Which means, if you're looking for me tonight, stop. I'll be in front of election results like it's my job. I love Tuesdays...

- Politico takes a look at what the midterms could mean for Nancy Pelosi, concluding that her she will be as strong as ever.

- The New York Times has its take.

Two unrelated notes:
- Five US troops were killed, when a NATO convoy was hit by a roadside bomber this morning. None of them was Adam, who emailed me this morning.

- And, to lighten it up, the North Carolina State baseball team apparently has a new name. While you are laughing at this unfortunate mistake, think about the intern, who has to take the sticker they order, and place it perfectly on the cover of thousands of media guide because of this screw up. Just sayin', don't forget the little people.

Finally, the most important information on election days.
- Philadelphia, PA - Probably not good for Specter, or Critz.
- Arkansas
- Kentucky

Happy Voting!