Known for his socially conservative views, the former Pennsylvania senator is a graduate of Carmel High School in Mundelein.
While Santorum was only there for a year, alumni of the Catholic school are already working for and against the presidential candidate.
Republican candidates for the GOP nomination for president have begun filing to get on the ballot for the Illinois primary in March. Friday is the deadline to file.
As Republican presidential candidate Rick Santorum works the crowd in New Hampshire, Al Salvi, honorary co-chair of the Illinois Santorum campaign, works he crowd at the Island Cafe in western Lake County.
With the help of his oldest daughter Katie, Salvi is collecting petition signatures for Santorum. Salvi, a former Illinois state lawmaker and candidate for U.S. Senate, says his sheets are filling up after Santorum's close 2nd place finish in Iowa.
"It was a little harder before - these people didn't know who he was - right now, he's got the momentum and so it's a good time for us to be gathering signatures," said Salvi.
Salvi is hoping there will be enough signatures statewide to get his fellow Carmel classmate on the Illinois ballot. While Santorum is a nearly-lifelong Pennsylvanian, his family moved to Lake County for one year - Santorum's senior year in high school.
Santorum graduated from the Mundelein catholic school in 1976, two years ahead of Salvi. The two never knew each other until years later, when Santorum campaigned for Salvi's 1996 bid for the U.S. Senate.
"He said, 'You know, I graduated from high school in Illinois'; I said, 'You're kidding,'" said Salvi. "I said, 'Where?'; he said, 'Carmel High School in Mundelein, Illinois'; I said, 'That's where I graduated from!"
Salvi and Santorum have much in common politically and personally: both have large families and are socially and fiscally conservative.
"He didn't go to Notre Dame - he's not perfect," said Salvi.
There are some Carmel alumni who say Rick Santorum is far from perfect. 2002 graduate Matt Muchowski has created a Facebook page called "Carmel Catholic Alumni Against Rick Santorum." Muchowski is against the candidate for his strong views opposing gay rights.
"Most my friends from Carmel are supportive of equality, and it was a shock that someone with such extreme views could come from our school," said Muchowski.
Muchowski says that so far, more than 30 Carmel alumni have liked his Facebook page.
Meantime, Salvi says that with the exception of two Illinois congressional districts, he is confident there will be enough Santorum signatures by Friday to get him on the ballot.
As Mitt Romney has the backing of the Illinois Republican establishment, Salvi is counting on grass-roots support for Santorum.