CHICAGO (CBS) — While the Democratic candidates for president make the rounds in South Carolina ahead of this weekend’s primary, some of them already have started reaching out to Illinois voters three weeks before they head to the polls.

CBS 2’s Vince Gerasole took a look at who’s shelling out the most money for your vote in Illinois.

Make no mistake about it, when the seven Democratic presidential candidates speak at Tuesday night’s debate in South Carolina, they realize they are on a national stage.

But if they are putting their money where their mouth is, Illinois isn’t on their radar, at least not yet.

Candidates are required to register their broadcast advertising spending with the Federal Communications Commission. It shows, since last fall, the candidates have spent nearly $18 million in broadcast ads in South Carolina. In Illinois, with a population more than double that of South Carolina, the candidates have spent $11.6 million on broadcast ads, but the primary here is still three weeks away, with delegate-rich Super Tuesday in between.

Political analyst Stephen Caliendo, a political science professor at North Central College, noted not all of the candidates now in the race will make it past Super Tuesday on March 3, when voters in 14 states will cast their ballots in the primary elections – including the two most populous states in the nation, California and Texas.

More than a third of the delegates up for grabs in the primaries will be decided on Super Tuesday.

Illinois doesn’t vote until two weeks later, but Caliendo said that doesn’t mean Illinois’ primary won’t count.

“It doesn’t mean that at all,”  Caliendo said. “Most of the campaigns have got to make sure they’re still going to be in the game by March 17th)

A deeper dive into ad spending reveals something else: in South Carolina, the numbers represent spending from the top seven candidates in the race; but in Illinois, they represent only three: former Vice President Joe Biden, former New York Mayor Michael Bloomberg, and billionaire Tom Steyer.

The spending is especially lopsided when you divide it up by candidate: Bloomberg has spent the vast majority, approximately $11.5 million; Steyer has spent about $100,000; and Biden has spent less than $1,000.

What’s harder to measure is online exposure to ads, which the FCC doesn’t track.

Online ads take a more personal approach in their plea for campaign donations; dollars that could be spent to sway Illinois voters as the state’s primary becomes more crucial in the weeks ahead.

A good performance by a particular candidate in Tuesday’s debate could change the money game. U.S. Sen. Elizabeth Warren performed so strongly at last week’s debate, she has raised $8 million since then.

Vince Gerasole