Mitt Romney is expected to win tonight in Illinois, and win big. It's a loophole primary, meaning that the presidential preference election is really just a beauty contest, with delegates selected directly. That is, the delegates will be on the ballot, and you can vote for Newt but then vote for Romney delegates. Anyway, I'd expect that if the polls are even close to correct, Romney will win the lion's share of the delegates, maybe close to a sweep (see the invaluable Josh Putnam for full details including the history -- as he says, it's called "loophole" because of long-replaced Democratic rules. Republican state parties, as always, have far more freedom to pick delegates however they want than Democratic state parties do).
I don't think I've made this point before, but while generally people have believed that the long slog is a disadvantage for Mitt Romney -- because he has to spend money now, and because he has to worry about very conservative voters who are sure to vote for him in November -- there's a flip side to that, too. First of all, as long as people are still reporting on these things, Romney gets lots of nights of being a winner. Granted, he's had a few losing nights, too, but overall more winner nights -- and if the nomination was over, he wouldn't be getting those. Moreover, ideological positioning does seem to matter, and while Romney has had to take issue positions which might hurt his perceived position, he gets to have weeks and weeks in which he's defined as the candidate of the moderates. Not to mention the other candidates practically calling him a RINO. That's how he wants to be perceived in November, and he's getting plenty of free publicity supporting the idea.
By the way, don't discount the possibility of a stampede after Illinois. I'm not making any predictions about it at this point, but if the delegates fall right for Romney tonight, it's going to be increasingly difficult for anyone to pretend that Romney's not going to get to 1144.