"Doing things the conventional way has never been my strong suit," Kerrey said in a statement. "This afternoon, I will file to become a candidate for the United States Senate in Nebraska. I came to realize that my previous decision was the easy one, not the right one.
"My commitment to serve Nebraska and America, and to be part of the debate about the challenges we face was too strong to dismiss. My family supports this decision 100 percent. I look forward to seeing you in the coming weeks. We have a lot of work to do."
Kerrey, governor of Nebraska from 1983 to 1987 and a U.S. senator from 1989 to 2001, said earlier this month he wouldn't enter the Senate race.
Nebraska Attorney General Jon Bruning, state Treasurer Don Stenberg, state Sen. Deb Fischer of Valentine and University of Nebraska Regent Chuck Hassebrook also have announced their candidacies, the Lincoln Journal Star said.
Kerrey registered to vote in Douglas County Tuesday and listed his sister's home in west Omaha as his official residence, the Omaha World-Herald reported.