"I'm tired after 45 years — emotionally — and I'm ready for change," Frank added.

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Speculation has it that Kerry could join the administration as either secretary of Defense or secretary of State, in which case some believe Sen. Scott Brown (R-Mass.) might run for Kerry's seat. Brown lost his seat earlier this month to Sen.-elect Elizabeth WarrenElizabeth Ann WarrenAre Democrats turning Trump-like? Manufacturing shrinks, raising questions for Trump Volatile presidential polls spark new round of anxieties MORE (D).

Frank dismissed the idea of running, and also deflected questions about whether he could beat Brown in a Senate race.

"That's not a relevant question," he told the Globe. "That's just hot-stove nonsense."

Frank reiterated that he wants to use his time away from Congress — the first he's had in 45 years — to write and speak about public policy and to teach.