The National Republican Congressional Committee is adding four candidates in uphill districts to its "Young Guns" program designed to boost challengers running strong campaigns.

The NRCC has added challengers Dan Debicella (R) and Mark Greenberg (R), who are running against Reps. Jim Himes (D-Conn.) and Elizabeth Esty (D-Conn.), respectively, in two Democratic-leaning districts.

They also included a pair of Republicans running in Democratic-leaning open seats: Elan Carr (R), who's running for retiring Rep. Henry Waxman's (D-Calif.) seat, and Bruce Blakeman (R), who's running for retiring Rep. Carolyn McCarthyCarolyn McCarthyWhy Congress needs an openly atheist member, now Lobbying World Lobbying world MORE's (D-N.Y.) seat.

All four have hit their fundraising goals but are running in blue-leaning districts that Republicans haven't been able to win in for some time.