Rep. Frank: 'Did you think I would serve till I was 106?'

"When I saw the new district there were two responses: One, that I'd think I'd win, but two, because it's 325,000 new people, it would mean almost full-time campaigning," said Frank on NBC's "Today" show Tuesday.

The Massachusetts congressman announced Monday that he would not seek reelection in 2012, ending the combative liberal’s three-decade career in the House.

Frank said he originally planned on retiring, but decided to remain in Congress to defend financial reform and push for a reduction in military spending as a part of deficit reduction. He said his decision changed when he learned of the new makeup of his district.

"I am making a personal decision here. I changed my mind because I felt I could spend these two years most effectively if I was a candidate for reelection … now that I would have to spend most of the year in campaigning, fundraising, et cetera, those reasons are no longer valid," said Frank.

He told NBC that his decision does not indicate a belief that Democrats won't take back the House and said he thinks another Democrat will win his seat.

"Did you think I would serve till I was 106? I mean, 71 years old … I have decided not to serve until three months before my 75th birthday. I guess I don't understand why that is so hard for people to grasp," he added.

Frank said he is proud of the work he accomplished throughout his career in Congress, but lamented the current state of the media and political institutions.

"It's gotcha this and gotcha that. It's gotcha journalism, it's gotcha politics and it does lessen our chances to get things done," Frank said.