As presidential campaigns fight over Midwestern battleground states, it may be troubling for Team Obama that the president’s lead over Republican rival Mitt Romney is about 30 percent smaller than his lead over Sen. John McCain, R-Ariz., in the 2008 election.

Obama leads Romney by 16 points (53-37) in Illinois, according to the Real Clear Politics average. The RCP average going into election day 2008 showed him leading McCain by 24.7 points (59-34). The final tally gave Obama a 25.1 point victory, as he carried his home state with 61.8 percent support, compared to McCain’s 36.8 percent.

“I believe what is happening in IL may be indicative of the rest of the country — Romney certainly won’t win IL, but Obama’s strength there may be more severely diminished than anyone outside of the state realizes,” Tom Elia of The New Editor, who wrote Poll Checker 2012 — a survey of national and battleground polls since 2000 — told The Washington Examiner.

Elia suggested that Obama’s weakness in Illinois relative to 2008 could be “a canary in the coal mine” for Democrats. We Ask America’s latest poll of the Illinois race also shows Obama with that 16-point lead — a commanding margin, in terms of the state itself, but down significantly from 2008.

“No matter how well Romney does in the five suburban “collar counties” or downstate (the rest of Illinois outside of Chicago, Suburban Cook & the Collars), the huge hunk of burning love that his home base provides the president simply cannot be toppled,” the polling firm observes.

The suggestion that Obama has lost support in Chicago suburbs is interesting given Michael Barone’s suspicion that Romney is making gains around the country among the suburban voters who historically vote Democratic.

“Mitt Romney seems to be running better in affluent suburbs than other recent Republican nominees,” Barone wrote this week. “That’s one reason he made big gains after the first debate in Florida and Virginia, target states where most votes are cast in relatively affluent suburban counties.”