Mitt Romney and the super PAC backing his candidacy, Restore Our Future, have spent almost $4 million on broadcast and cable ads in Illinois, according to the latest media buy information.

Meanwhile, Rick Santorum and the super PAC backing his bid–Red, White and Blue Fund–purchased $530,111 in television time in the state. That equates to a 7-1 spending advantage for Romney.

A majority of the ad spending has been concentrated in the Chicago area since the city and its suburbs comprise a sizable portion of the electorate where Romney needs to do well in order to win the state.