Freshmen to watch

Sen. Kelly Ayotte (R-N.H.)

Ayotte, one of Sarah Palin's "mama grizzlies," was the only woman elected to the U.S. Senate in 2010. A former state attorney general, she defeated a tea-party-backed candidate in the GOP primary and then Rep. Paul W. Hodes (D-N.H.) in the general election to keep retiring Sen. Judd Gregg's seat in Republican hands.

Sen. Chris Coons (D-Del.)

Coons is best known for defeating Republican Christine O'Donnell, who famously declared "I am not a witch" in a campaign ad. He was a volunteer for Ronald Reagan's 1980 presidential campaign and became a Democrat after spending a year in Kenya during college. Coons fills the seat vacated by Vice President Biden.

Sen. Marco Rubio (R-Fla.)

Rubio has long been singled out as a rising conservative star, even forcing Florida Gov. Charlie Crist out of the GOP Senate primary to run as an independent. Rubio is the only Republican senator of Latino descent, and party leaders will be counting on the fresh face to reach out to Hispanics, who are crucial to building the GOP brand.