Tonight: 3 Primaries, 7 Things You Need to Know

You've probably heard this before, but today's Republican primaries in Wisconsin, Maryland, and DC are pretty important. They'll surely push Mitt Romney past the 600 delegate mark (does that make it "halftime"?), and they represent Rick Santorum's last chance to win a Midwestern state, Politico reports. Here's what you need to know:

• Wisconsin is what matters: It doesn't award very many more delegates than Maryland, but Maryland is guaranteed to go blue in November, whereas Wisconsin is a swing state, ABC News points out.

• Romney's the favorite… Polls show he could sweep both states; indeed, Wisconsin conservative radio host Charlie Sykes is asking if Romney can win by double digits.
• ...and a conservative darling? In Wisconsin Romney has support from "the entire conservative infrastructure of the state," Sykes says, including Paul Ryan and Ron Johnson. This could be a chance for him to finally score well with self-proclaimed "very conservative" voters.
• Bought and paid for: Of course, Romney has spent handsomely to secure his lead; he and his allies have poured $3.1 million into Wisconsin TV ads, about four times what Santorum and co. have spent.
• Scott Walker is watching to see how strong turnout is. Turnout is expected to be the key to his June 5 recall election, so today's primary represents a sort of early test for the GOP machine.
• No one bothered polling DC but everyone pretty much assumes Romney will win. Both because he's the establishment favorite, and because, well, Santorum didn't get his name on the ballot.
• Newt Gingrich is still here: Though you'd be forgiven if you didn't notice—his campaign is "near-suspended," traveling and spending very selectively, according to Politico. He's focused mainly on Maryland, and needs to post a respectable percentage to justify continued press attention.

(More Wisconsin stories.)