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With three projected victories on Tuesday night, Mitt Romney is poised to effectively win the Republican nomination to be his party's candidate to compete against President Barack Obama for the White House in November.
With poll numbers on his side and a string of endorsements from GOP bigwigs calling for the party's drawn-out campaign to wrap up at last, a strong win in Wisconsin would show Romney has considerable appeal in a key swing state that holds a winner-take-all 42 delegates and helped propel Sen. John McCain to the nomination in 2008.
Republican rival Rick Santorum lags behind in delegates but is hoping for an upset like he pulled off in two Southern states, Mississippi and Alabama.
We're feeling good, Santorum said at a rally Monday at a bowling alley in Menasha, ABC's Arlette Saenz reported. We're feeling like we might pull off an upset here tomorrow in Wisconsin. What do you think?
Considering the large gap in the polls, however, an upset is unlikely. According to an NBC News/Marist poll taken from March 26-27, Romney was in the lead with 44 percent, compared to Santorum's 33 percent, Texas Rep. Ron Paul's 11 percent and former House Speaker Newt Gingrich's 8 percent.
A Public Policy Polling survey taken Saturday and Sunday had Romney in the lead with 43 percent to Santorum's 36 percent. Romney garnered 44 percent to Santorum's 34 percent in a Rasmussen Reports poll taken on Thursday.
Romney's lead in the polls is still not as big as McCain's win in 2008, in which he took about 55 percent of the vote.
Forty-two delegates are up for grabs in the state, which is holding its contest the same day as Maryland and the District of Columbia. A total of 96 delegates are at stake on Tuesday.
Wisconsin awards all of its delegates to the winner, meaning second place counts for nothing.
All four candidates have been stumping in Wisconsin for the past week. Romney had Janesville native and House Budget Committee Chairman Paul Ryan, on his side. Ryan's is one of several strategically announced endorsements that have come through for Romney in the past couple of weeks.
The Wisconsin Republican called for the Republican Party to unite behind Romney so it can focus on beating President Barack Obama in the fall. Ryan told the Milwaukee-Wisconsin Journal Sentinel that the Republican race is getting to the point where it's going to become counter-productive if the primary drags on.
Sen. Marco Rubio of Florida also chided Romney's rivals for banking on the strategy of a floor fight in Tampa in August because that's a recipe of four more years of Barack Obama. Former Florida Gov. Jeb Bush also encouraged Republicans to unite behind the front-runner.
In another sign that the GOP establishment is pushing for a Romney nomination, the Republican National Committee plans to begin raising money with Romney this week, reported the Wall Street Journal.
Below is everything you need to know to keep track of the results tonight:
When to Start Watching: Wisconsin polls close at 8 p.m. CDT, or 9 p.m. EDT. Results will begin rolling in county by county throughout the rest of the night. Media outlets will call the winner if the outcome is clear; if it's not, it may be a long night. Romney was called as the winner in Arizona, for example, almost immediately after polls closed on Feb. 28, while in Mississippi on March 13, Gingrich, Romney and Santorum were all within a single digit of each other -- for three hours.
Counties to Watch: The majority of primary voters are from Milwaukee and its suburbs. In 2008, 43 percent of Wisconsin voters came from Milwaukee County, according to the Milwaukee-Wisconsin Journal Sentinel. Twenty-one percent of 2008 primary voters came from Green Bay, making about two-thirds of primary voters from those two areas. That's good news for Romney, who tends to do well in those suburban communities that tend to be more affluent and well-educated.
Where to Watch Live: CNN will be reporting updates of the the Wisconsin primary Tuesday night, with some coverage streaming live on live.cnn.com. Fox News' Illinois coverage can be found online at live.foxnews.com.
Politico's new live show will feature reporters talking about the results as they come in. You can catch Politico Live beginning at 7 p.m. EDT on C-SPAN, www.politico.com/livestream and Politico's iPad and iPhone apps.
Where to Get Live Results: Google is always a reliable source in getting the most updated numbers coming in from a primary.
How to Get Results on Twitter: Search for the hashtag #WIprimary to follow the conversation about Wisconsin. You can also look at this list of campaign staff, reporters and pundits for live commentary on the contest: https://twitter.com/#!/sara_dover/politics