U.S. Sen. Mark Kirk's ex-wife files FEC complaint about campaign payments to his girlfriend

At the heart of the matter is Vertolli's assertion that the Kirk campaign may have improperly hidden money to McCracken by paying her through another company working for the campaign. Because the money was not paid directly to McCracken, her name does not appear in Kirk's federal disclosures.

Experts consulted by the Tribune said it's unclear how the FEC will view that arrangement, but they wondered why the campaign didn't simply hire McCracken or her firm directly. One Washington lawyer who handles election law said that generally speaking, "intentionally obscuring the actual payee of a campaign expenditure is a violation."