Illinois Gov. Pat Quinn (D) (Seth Perlman/AP)

The key to Illinois Gov. Pat Quinn’s chances this November could be … Barack Obama?

A new study finds that, over the past century, the president’s party has won his home state’s gubernatorial race four out of five times. That’s good news for Illinois Gov. Pat Quinn, who is engaged in one of the nation’s toughest gubernatorial battles.

Quinn is facing wealthy venture capitalist Bruce Rauner (R), who broke the state’s record for self-financing a gubernatorial campaign when his out-of-pocket spending hit $6 million in March, even before his successful primary win. The Chicago Tribune reported at the time that he is “perhaps the wealthiest candidate ever to run for public office in Illinois.” And that ability to spend and raise large amounts has Republicans optimistic about his prospects.

Rauner has enjoyed slight leads over Quinn in multiple polls. But the fact that Quinn has a fellow Illinoisan in the White House could be a sign that he may eke out a win, according to the study conducted by Eric J. Ostermeier, a research associate at the University of Minnesota Humphrey School’s Center for the Study of Politics and Governance.

As with any such study, the sample size was notably small and the time horizon notably long: Ostermeier found that of the 30 gubernatorial races since 1913, all but six have gone to the nominee of the sitting president’s party.

Only two of those six losses occurred in the past half-century, though: Incumbent Republican Mike Huckabee won easily in Arkansas in 1998 while Democrat Bill Clinton was in office; and Democrat Ann Richards won in a tight race in Texas during President George H.W. Bush’s time in the White House. Before Richards, the sitting president’s party won the gubernatorial race in his home state in ten consecutive elections.

A recent Gallup poll found that Obama enjoyed a 53.7 percent approval in Illinois, one of 11 states where the rate was above 50 percent. Quinn has made known to the White House that he would like the president’s help, though it’s not clear if he’s made a formal ask for assistance. But Obama’s very presence in the White House could be a good sign for Quinn.

Reid Wilson contributed.