Shadegg's campaign made four payments to Sidley Austin -- which once employed Barack and Michelle Obama in its Chicago office -- between July and September, according to federal campaign filings. The firm has a wide-ranging practice that includes business law and white-collar criminal defense.
"It is not a criminal matter," said Shadegg spokeswoman Abby Winter, when asked about the purpose of the payments. "The congressman is considering taking legal action against a party. It has to do with libel and slander."
Winter refused to answer any other questions about the case. A call to the firm wasn't returned.
Shadegg, 59, is locked in an acrimonious re-election battle with Democrat Bob Lord.