Tuesday's votes in Michigan and Arizona are "make or break" for Mitt Romney according to everyone, even if few think any combination of loss and victory for the candidate would actually end the Republican primary. Michigan polls show Romney and Rick Santorum within just a couple points of each other, and Santorum is trying to get an advantage by encouraging Democrats to vote for him -- even if they'd do so only because they think it would hurt Republicans. We'll be liveblogging the returns -- which come in for both states at 9 p.m. Eastern time -- and the exit polls, starting at about 8:30 p.m. Be sure to comment!

Updates:

11:00p.m.: With 84 percent of precincts reporting in Michigan, Romney has 41 percent to Santorum's 38 percent. Paul has 12 percent and Gingrich is way in the back with 7 percent. He easily won Arizona. Pundits declared Michigan a crucial test for Romney. He passed.

What Romney did tonight is kind of like the gymnastics gif to the left. Was coming from behind to win in his homestate -- despite multiple trips over his own tongue -- as hard as the reverse plange pictured? Maybe not physically. But spiritually? Emotionally? Strategically? Romney might not have won the Olympics tonight, but he's definitely the top athlete going into Trials.

Michigan was only the latest "test" for Romney, according to lots of analysts tonight. New Hampshire, Florida, Nevada were all tests too. The next test? Ohio. Tonight was merely a "bullet dodged" Fox News says. The conventional wisdom on MNSBC is that we have to wait to Ohio to know for sure that the Republican primary is over.

10:48p.m.: In his victory speech, Romney says that pundits counted him out. This is incorrect.

1042:p.m.: Again returning to the Republican Party's demographic problem, note the strategically placed black couple over Romney's left shoulder.

Then, mid-speech, some white dude steps in front of them, talks to them briefly, and then starts checking his BlackBerry:

It seems unlikely a staffer would wear a tan suit. On the other hand, who but a staffer would charge in front of them like that?

10:37p.m.: Romney looks pretty pleased:

10:34p.m.: Ann Romney: "Thank you Kid Rock!" She sounds just a little nervous.

10:29p.m.: And now we turn to Romney HQ:

10:27p.m.: Maybe it's just the quality of the microphone, but Santorum sounds really breathy tonight.

10:25p.m.: Santorum is stealing from Gingrich like mad tonight. First he claims he authored welfare reform. Now he's stealing a classic Newt move: props. Santorum has brandished both a piece of shale and a copy of the Constitution. We can only hope he'll finish with a woman walking on a treadmill.

10:18p.m.: Santorum's daughter is very expressive. It's pretty clear she knows her dad has lost tonight.

10:14p.m.: NBC News calls Michigan for Romney.

10:12p.m.: As Santorum gives his probably-concession speech, a man shouts "We love you!" Santorum says that people have gotten to know him, if "not exactly through the mediums I want you to get to know me."

10:04p.m.: Unlike in several votes this year -- FloridaMinnesota -- Romney is doing better than he did in 2008 in most Michigan counties, The New York Times' Nate Silver points out.

10:01p.m.: Booze is allowed a Romney's election party, which is looking more and more likely to be a victory party.

9:56p.m.: Somewhat surprisingly, Santorum won all age groups under 65 in Michigan. Romney won the old folks 48 percent to 31 percent. You think of Ron Paul as the young person's candidate, but you don't think of Santorum as the middle-aged person's candidate.

Paul only got 20 percent of those aged between 30 and 39. Only 10 percent of the electorate was younger than that, so the exit polls don't measure how they voted.

9:53p.m.: With 57 percent of precincts reporting, Romney has 40 percent to Santorum's 36 percent, CNN reports.

9:47p.m.: Given Jonathan Chait's story discussing the Republican party's impeding demographic doom in New York this week, it's amusing that the number of black, Asian and Latino folks voting in the Michigan primary was so small, the exit polls couldn't accurately estimate by what percentage they went for each candidate.

9:44p.m.: On MSNBC, Tom Brokaw calls Mitt Romney a "young man." And they say show business is only for the young. (That is a thing they say, right?)

9:43p.m.: Continuing to speculate about Gingrich's campaign funds, you can't help but note the terrible lighting and awful audio at this Gingrich speech in Georgia:

9:41p.m.: Note the handmade pro-Newt sign -- a heartfelt sign of devotion or a sign of a lack of money?

9:39p.m.: Ron Paul refers to Santorum's charge that Paul and Romney have a pact to attack the senator as "someone who believes in conspiracy theories."

9:34p.m.: A national poll earlier this week found Santorum faced no gender gap. But in Michigan, Romney did much better among women than men, according to CNN exit polls. Among men, Romney won just 39 percent to 38 percent. But among women, he won 42 percent to Santorum's 37 percent.

9:32p.m.: "Look on the bright side, conservatives. The UAW wanted Santorum to win. You beat 'em!," Slate's Dave Weigel tweets.

9:30p.m.: A pretty adorable moment between the Santorums in Michigan today:

(Photo via Associated Press.)

9:22p.m.: Given Santorum's very good performance among Democrats voting in the Republican primary (50 percent voted for the former senator), Romney's campaign is going to keep talking about the Santorum campaign's robocall urging Democrats to pick Santorum, BuzzFeed's McKay Coppins reports. They'll accused Santorum of "supporting the liberal Democrat line against" Romney.

9:20p.m.: Of those who want illegal immigrants to be deported, 43 percent voted for Romney, Fox News reports. Of evangelical Christians, 38 percent voted for Santorum, while 33 percent went for Romney.

9:18p.m.: With 30 percent of precincts reporting, Romney is ahead 41 percent to 38 percent.

9:13p.m.: The candidates might not want to be associated with George W. Bush, but not all their fans feel that way. A woman wears a Bush shirt at Romney's election night party:

(Photo via Associated Press.)

9:10p.m.: More from exit polls: 40 percent of Michigan primary voters supported the Detroit bailout.  Electability was the top issue for the plurality of voters, 33 percent. Strong character was most important for 23 percent, and being a true conservative was the most important thing in picking a candidate for 15 percent.

9:02p.m.: Victory in Arizona, Wolf Blitzer says, is "nothing to sneeze at." Exit polls show he easily won "somewhat conservative" voters, as well as moderates. He won those who picked the economy as the top issue, 49 percent to Santorum's 28 percent. 

But Santorum won half of "very conservative" voters.

9:00p.m.: CNN calls Arizona for Romney, giving him about 44 percent. He gets 29 delegates. Michigan is too close to call.

8:58p.m.: CNN reports Santorum did get a teeny bit of benefit from liberal pranksters voting in Michigan. 10 percent of the voters were Democrats, and half of them went for Santorum. That's a net gain of 3.5 percent for the former senator.

8:46p.m.: Ron Paul speaks early and spends a lot of time talking about foreign policy -- "nonintervention." He says, "It eliminates all our goodness if we think we have the authority to go overseas and tell people how to live." Huge cheers follow.

And Paul becomes the second Republican presidential candidate this week to make a reference to John F. Kennedy, but unlike Santorum's, Paul's is a positive one. He approvingly notes Kennedy decided not to nuke the Soviets during the Cuban missile crisis.

8:42p.m.: With 5 percent of precincts reporting in Michigan, Santorum is ahead of Romney, 40.4 percent to 38.5 percent.