Mitt Romney won the Illinois GOP primary on Tuesday night, but some took issue with how much money he spent to achieve that victory.

Polls taken last week seemed to indidcate the race would be close in Illinois, but the final result was a difference of almost 20 percentage points between Romney and his closest opponent, Rick Santorum.

Romney and Restore Our future, a super Pac that backs him, outspent Santorum and a super PAC that supports him by $3.5 million to $500,000, a cash advantage of 7-to-1.

One ad accused Santorum, a former U.S. senator for Pennsylvania, of changing his principles while serving in Congress. Two ads slammed Santorum for raising the debt ceiling and legislative pay while he was a lawmaker. Another accused him of siding with former U.S. Sen. Hillary Rodham Clinton to support legislation allowing felons the right to vote.

Restore Our Future already has allocated more than $2 million for in television advertising across Wisconsin. Santorum has spent about $50,000 to combat those ads.

Gingrich pounced on the cash difference Tuesday night.

"To defeat Barack Obama, Republicans can't nominate a candidate who relies on outspending his opponents 7-1. Instead, we need a nominee who offers powerful solutions that hold the president accountable for his failures," Gringrich wrote in a statement.