Wisconsin’s primary Tuesday is Rick Santorum’s last best chance to keep Mitt Romney from walking away with the nomination.

While the latest PPP poll shows Santorum trailing by 7 points, he’s outperformed his poll numbers before, and low turnout could help him close the gap. Enthusiasm for the race has been muted as Romney has bombarded the state with advertising and as Wisconsinites have been more excited about the recall election for Republican Gov. Scott Walker (along with the lieutenant governor and four state senators) later this spring. With a three-week hiatus after today’s contests (Maryland and Washington, D.C., are also voting, and Romney is expected to win both contests), Santorum has virtually camped out in Wisconsin, seemingly going bowling every day, and even gave his Louisiana election-night victory speech in Green Bay.

Here are four things to watch in Wisconsin as the returns come in Tuesday night:

Suburban Milwaukee

One of the chief battlegrounds on Tuesday night will be suburban Milwaukee, an area the Romney campaign is focusing on. While the Milwaukee burbs may seem similar to the “Collar Counties” that Romney won overwhelmingly in Illinois two weeks ago, there are big differences. Suburban Milwaukee is a Republican stronghold, the cornerstone of which is Waukesha County, an area so Republican that John McCain won it over Barack Obama by 25 percentage points in 2008, despite losing statewide by 7 points. This area will be a crucial battleground and one that Romney needs to win to balance out Santorum’s strength in rural areas.

Evangelicals

The clearest indication of how well Rick Santorum does in a given Republican primary is the percentage of evangelical voters participating. Evangelicals have made up more than half of the electorate in all 10 states where Santorum finished first. Romney, on the other hand, has yet to win a state where evangelicals made up a majority of voters. While Wisconsin has a relatively low percentage of evangelicals compared to many other Midwestern states, evangelicals made up an outsize 41 percent of the Republican electorate in the PPP poll, a danger sign for Romney.

Attention Deficit

The Republican contest has already gone on for almost a year, and Wisconsin’s primary will also mark the three-month anniversary of the Iowa caucuses that began the voting season. The national press has largely moved on to other stories, which is good news for Mitt Romney, who as the frontrunner has little to gain from a Wisconsin win, but having outright predicted victory here, a loss would put the press back on the scent of the primary and give new life to Santorum. Wisconsin voters have been more concerned with the recall than the presidential contest, which has come off like a down-ticket contest. There’s a reason Mitt Romney didn’t thank volunteers at one of his campaign’s phone banks, but instead did so at one of Scott Walker’s.

Delegate Count

While Wisconsin may be relatively close in terms of the total number of votes for each candidate, expect the delegate count to be lopsided. The state awards three delegates to the winner of each of its eight congressional districts, but gives 21 delegates to whoever wins a plurality of the popular vote. A close second, like he ran in Ohio, won’t do Santorum much good here. With Santorum making clear that he’ll drop out if Romney hits the magic number of 1,144 delegates, he needs a win to keep the former Massachusetts governor from edging closer to the nomination.