This was a big issue before the newest class of lawmakers took office. They didn't have enough "yes" votes then, but now they say they do.
Lawmakers supporting same-sex marriage say it was never a matter of "if" but "when." They say they want to wait until they're sure it will pass, instead of having it shot down.
Now, Senate President John Cullerton says he has the votes to get it passed. Gay rights advocates say it couldn't come on a better day.
New polling data shows nearly half the country supports gay marriage. Supporters hope those numbers will boost this bill's chances.
If it does pass the senate on Valentine's Day, it would still have to go through the house and then to the governor. It's already seen a lot of support in both of those places.