By the time Republican primary season got around to Illinois in past election cycles, the Land of Lincoln was pretty much an afterthought since the party's nominee had already been decided. Not this time.
Mitt Romney has what seems like an insurmountable lead in delegates. But there are questions as to whether he can reach the 1,144 needed for the nomination by the party's August convention. And with his rivals, especially Rick Santorum, refusing to exit the race, the GOP primaries have entered the grind-it-out-for-every-delegate phase.
That means that Illinois, all of a sudden, counts plenty. To a certain extent, it has even become Romney's new firewall. If he can achieve more than a narrow win in Illinois and lay claim to most of the state's 54 delegates, he will increase the pressure on Santorum to call it quits so Romney can focus his fire on President Obama.
Not that Santorum would actually leave the race even if he lost badly in Illinois. But a strong Romney showing would certainly give the front-runner in delegates, and others in the party, more leverage as they turned the screws on the former senator from Pennsylvania.
But if Santorum can keep Illinois close or, to the horror of Romney and the party establishment, even prevail, the former Massachusetts governor's weaknesses as a candidate would be further reinforced.
That could only be bad news for a candidate once thought to have a lock on his party's nomination.
Thus, just as on other Tuesday evenings since January, there could be real drama, this time in Illinois.
Here are three things to watch for:
Turnout — If the upscale and college educated voters in Chicago's collar counties — DuPage, Kane, McHenry, Will and Lake and go to the polls Tuesday in large numbers, it should be Romney's night and not by a little bit.
Illinois has a larger percentage of Republicans who are wealthier, especially with household incomes over $200,000 than Michigan and Ohio, which should benefit Romney.
But if Republican voters turn out strongly in the more socially conservative "downstate" Illinois, which in many ways have more in common with the American South than the North, Tuesday's contest could be a lot closer than many people predict; Santorum could even hand Romney another defeat, the first in one of the large industrial northern states that were supposed to be Romney's bulwark.
The evangelical vote — Voter surveys in other states like Mississippi and Alabama tended not to give enough weight to the evangelical segment of likely Republican voters. That has resulted in the strength of Santorum's support prior to the actual primaries being understated.
Illinois's Republican Party doesn't include as high a percentage of evangelical voters as Ohio or Michigan. But a strong turn out by evangelicals downstate could signal a worrisome night for Romney.
The Tea Party influence — While its Republican Party has a tradition of moderation, Illinois Republicans have every so often gyrated towards the more conservative candidate. And that was even before the emergence of the Tea Party.
But Tuesday will be the first presidential primary in the centrist Midwestern state in the Tea Party era, a time during which Illinois' Republicans have grown more conservative, according to analysts.
The Tea Party factor could give Santorum an edge, especially in counties where he and Romney may be in a tight race.
But Romney has also won significant percentages of Tea Party voters in other states, like Florida for instance. So it's not clear at all how the presence of the Tea Party will play out in Illinois which is why it bears watching.