The opinions expressed below are Jon Keller's, not those of WBZ-TV, CBS News or Paramount, a Skydance Corporation.

Longtime incumbent Republican Maine Senator Susan Collins has a new challenger: the state's Democratic Governor Janet Mills .

Mills promises to be a one-term senator

Governor Janet Mills has announced her intention to run in next year's midterm election. But there's a twist to Mills' candidacy that highlights the backlash against aging politicians.

Remember last winter when the 78-year-old governor clashed with our 79-year-old president over banning transgender athletes?

"You better do it because you're not going to get any federal funding if you don't," Donald Trump warned Mills during a White House event with governors.

"I'll see you in court," replied Mills, and

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