Campaign spending in the Kentucky Senate race between GOP Sen. Mitch McConnell and Democrat Alison Lundergan Grimes could reach $100 million. LM Otero/AP hide caption

itoggle caption LM Otero/AP

Senate Republican leader Mitch McConnell speaks to supporters Saturday at the Tanglewood Farms Restaurant in Franklin, Ky. McConnell faces Tea Party challenger Matt Bevin and several other lesser-known candidates in Tuesday's GOP primary. Timothy D. Easley/AP hide caption

itoggle caption Timothy D. Easley/AP