Smith told Manchester TV station WMUR Sunday that he previously stayed out of the race to allow room for other candidates. He said he gave into encouragement to run when no other major candidate materialized for the GOP.
There are already two other Republicans in the race, according to WMUR: former state Sen. Jim Rubens and activist Karen Testerman. Prominent national Republicans also have been encouraging former Massachusetts Sen. Scott Brown to run for Shaheen's seat.
This post has been updated.