Here's the backstory behind Chuck Grassley and Lois Lerner

Here's the backstory behind Chuck Grassley and Lois Lerner | WashingtonExaminer.com:
"By the time Lois Lerner suggested auditing Sen. Chuck Grassley in a Dec. 4, 2012, email, the Iowa Republican had spent five years scrutinizing Lerner's IRS division.
Grassley, during his tenure as top Republican on the Senate Finance Committee, zeroed in on abuses by charities and other nonprofit groups improperly claiming tax-exempt status under Lerner, and he spearheaded a 2006 change in federal law making it harder for organizations to improperly claim the credit.

Grassley and Lerner were no strangers to each other, and it’s one of the reasons Republicans fear Lerner’s push to audit Grassley might have been politically motivated.
“If she was interested in political payback, it would be absurd,” Sen. Rob Portman, R-Ohio, a member of the Senate Finance panel, told the Washington Examiner.
“What Senator Grassley was trying to do all of those years was to make sure that people who had tax-exempt status deserved it.
He was working with the IRS in a way, not against them.”
Congressional staff who worked under Grassley during his 2001-10 tenure as top Republican on the Senate Finance panel say he conducted vigorous oversight of the IRS Tax Exempt division, which Lerner was appointed to run in 2005.
“This isn't random,” said Dean Zerbe, a tax lawyer who helped Grassley investigate tax-exempt groups and reform the law governing them. 
“This is going after the senator most active in conducting serious reviews of charitable organizations as well as the IRS work in this area."
...In December 2012, Lerner mistakenly received an invitation to an event that was meant for Grassley. The event officials offered to pay for the senator's wife to attend the event.
Lerner asked (via e-mail!!!) a co-worker, “Looks like they were inappropriately offering to pay for his wife. Should we refer to Exam?”
...Ways and Means Committee Chairman Dave Camp, R-Mich., said he suspected Lerner's motives to refer Grassley for an audit were political.
"I think clearly we have problems with the IRS' role in politicizing that agency when a Republican senator, simply because they received an invite, is referred for a tax audit,” Camp said.