Voters head to the polls in four states today, with Kansas, Michigan, Missouri and Washington state all holding their primaries.

On the ballot: Missouri Republicans could nominate a less-than-desirable Senate candidate, we’ll get a preview of the open Washington governor’s race thanks to that state’s blanket primary and in Detroit we could see a white congressman win a majority-black district today for just the second time.

Here are five things to watch for:

1. The Akin effect

Rep. Todd Akin (R-Mo.) announces his candidacy for the Senate in Creve Coeur, Mo.(AP Photo/Jeff Roberson)

Conventional wisdom has it that Republicans would prefer their Senate nominee to be, in order: 1. John Brunner. 2. Sarah Steelman. 3. Rep. Todd Akin. The question is how much the latter two, and particularly Akin, would jeopardize what looks to be a great pickup opportunity for the GOP against Sen. Claire McCaskill (D-Mo.).

The latest polling of the race shows Brunner leading, but it’s anybody’s ballgame, and Akin appears to be the momentum candidate (what’s more, his base, religious conservatives, may be the most reliable voter bloc). Democrats seem to think getting Akin through the primary would do wonders for them, and they’ve spent a bunch of money in the GOP primary trying to make that happen. The congressman gives them an opening as someone who is very conservative, doesn’t have a history of tough campaigns, isn’t terribly compelling personally and, perhaps most notably, has declined to go negative in his campaign. That could be a recipe for success for McCaskill.

But what we’re forgetting here is that basically none of these candidates has set the world on fire, and the reason the GOP can beat McCaskill is that she’s in such a bad position right now. Second-tier candidates can win in good situations; Sens. John Boozman (R-Ark.), Jeff Merkley (D-Ore.) and Kay Hagan (D-N.C.) all underwhelmed or came from meager beginnings early in their campaigns but eventually went on to win.

That said, all of them turned out to be capable candidates in the end; the onus would be on Akin to prove himself This is a seat the GOP is counting on to retake the majority, so make no mistake: today’s result matters.

2. Hoekstra’s lot

Former congressman Pete Hoekstra has run into a little trouble in his GOP Senate primary, but all indications are that he has held steadily to his lead in a field that, luckily for him, is a little bit crowded.

That said, Hoekstra hasn’t acquitted himself terribly well for the general election, including running a controversial Super Bowl ad and then stumbling into a bit of a birther pickle. EPIC-MRA, which polls this race frequently, last week showed Stabenow extending what had been a single-digit lead out to 14 points.

But Hoekstra is someone who, until this primary season, was seen as a pretty serious politician who could win if everything falls into place. And a big primary win could cure a lot of ills.

Either way, though, this is very much a third-tier target for the GOP. If Hoekstra wins, it’s likely because of a huge GOP wave nationally or a huge problem for Democrats in blue-leaning Michigan.

3. Inslee vs. the blanket primary

The Fix loves blanket primaries. Let’s just get that out of the way right now. When all candidates are thrown into one giant primary, it allows for instant analysis about which side got more votes and who is better-positioned for the general election.

That said, it’s not foolproof.

Democrats point out that Republicans will frequently get a higher percentage in the blanket primary than they will in the general election. And given the fact that polling is pretty close in the open Washington governor’s race, that means it’s quite possible state Attorney General Rob McKenna (R) will get more votes than former congressman Jay Inslee (D), despite the state’s blue lean.

That doesn’t mean Inslee’s going to lose, though. Democrats point out that Inslee himself lost by six points in a 1998 House primary but then won the general election by the same margin. The same thing happened to Rep. Rick Larsen (D-Wash.) last year. And in the 2008 governor’s race, Gov. Chris Gregoire (D) defeated Republican Dino Rossi by just two points in the primary but by six in the general election.

That said, if McKenna gets more of the vote, it’s going to confirm what we already knew: This is a competitive race.

We don’t expect tonight to change that perception, although a decent-sized Inslee win or a big McKenna win could change perceptions of where the race is at right now.

Also worth watching: The crowded field in the open 1st District, where a bunch of Democrats are fighting for the right to face Snohomish County Councilman John Koster , the only Republican in the race. Also watch for how close to 50 percent Koster gets.

4. The member-versus-member primaries

One tough consequence of the decennial redistricting process: For some members in states with shifting populations, the only path to another term is defeating a fellow member of the delegation from the same party. If, as expected, Rep. Gary Peters (D-Mich.) wins his intra-party battle against freshman Rep. Hansen Clarke in Michigan’s 14th District, he will almost definitely join Rep. Steve Cohen (D-Tenn.) as just the second white member of the House to represent a majority-black district.

By working to boost turnout in the familiar parts of his district, lining up support from organized labor and making inroads on new terrain, Peters has put himself in a good position to defeat Clarke and the rest of the field. During the primary, race has been an undercurrent, with the half-black, half-Bangladeshi Clarke crying foul over tactics he said were “designed to do is to split up the black vote.” Either way, Clarke has been significantly out-hustled but Peters, who should be in line for the next big statewide opportunity in Michigan after his performance here.

Missouri will play host to another member-versus-member primary, pitting a white candidate against a black candidate in a majority-minority district. The campaign between Democratic Reps. Lacy Clay and Russ Carnahan has been tough for Carnahan, who is competing on mostly new terrain. Clay is expected to defeat the son of the late-Sen. Mel Carnahan, who was angry with his Democratic colleagues for sacrificing him to save themselves.

5. McCotter’s vacancy

Now-former congressman Thaddeus McCotter’s (R-Mich.) inability to collect enough valid signatures to get on the ballot ensured he would not return to Congress next year, setting off an 11th-hour scramble for his seat.

Unimpressed with the only Republican on the ballot, Ron Paul-aligned long-shot Kerry Bentivolio, local party power brokers got behind former state senator Nancy Cassis, who is one of three candidates waging a write-in bid on the GOP side. It may take until dawn arrives on Wednesday morning before have a winner on the GOP side, due to the time-consuming process of combing through write-in ballots.

On the Democratic side, physician Syed Taj has been endorsed by local party leaders and Sen. Debbie Stabenow, and he is the clear establishment choice and most electable general election option. But to get that far, he has to get by activist Bill Roberts, whose views on some issues would make him general election vulnerability for the party. If Cassis and Taj win, it’s an uphill climb for Democrats to pick up the seat; if it’s Bentivolio versus Taj, things could get interesting.