Experts were surprised when presidential candidate Rick Santorum released four years of tax returns this week.  Although he earned less than his republican rival Mitt Romney, he paid at a higher rate.

The details of his tax records showed that he and his wife Karen earned more than $3.7 million over the last four years (2007-2010) and paid almost one-quarter of it in income tax.

He made his millions as a corporate consultant and a media commentator after serving as Senator of Pennsylvania.  His earnings jumped from $600,000 in 2007 to $1.1 million in 2009. His 2010 tax return showed his income as $923,000.

In 2009, Santorum’s income tax rate was 28% while Mitt Romney only paid an effective income tax rate of 13.9% on earnings of about $27 million.

The release of Santorum’s tax returns could affect his campaign. During his campaign, Santorum has claimed to have close ties with middle-class blue collar Americans.

Expect to see Mitt Romney use Santorum’s tax records against him. He’ll try to label him as a “Washington insider” and not a friend of the working class.