Barbara Boxer, who represented the Bay Area 6th District immediately south of Riggs' before winning her Senate seat in 1992.

CNN: Rep. Riggs To Run For Senate

The high-stakes battle in Kentucky's 6th District, crucial to Republican hopes of retaining a seven-seat House majority, matches two political veterans with voting records that can be attacked and record-smashing amounts of money to spend.

CNN: Bitter U.S. House battle in Kentucky horse country