Image copyright Getty Images Image caption Vermont senator Patrick Leahy announced he would not seek re-election
Democratic Vermont Senator Patrick Leahy is retiring at the end of his term and a Democrat-backed candidate has started campaigning to replace him.
Vermont state senator Peter Welch says he wants to move the state “forward, not backwards”.
He is challenging Governor Phil Scott for the Democratic nomination.
But fellow Democrat, former Governor Howard Dean, has ruled himself out, saying he does not want “to spend three years commuting from the Cape”.
Vermont and the surrounding Congressional District held by Mr Leahy for more than 20 years is solidly Democratic and backed by voters over Donald Trump.
Mr Scott would become the first independent to hold the office since it was created by the US Constitution in 1912.
A former Burlington mayor and failed candidate for governor, Mr Welch has worked to raise $800,000 (£585,500) in campaign funds and says his efforts have “hit a ceiling” so far.
An opinion poll in March showed voters trusted him as the most capable candidate to break with President Trump by more than two to one.
The Democratic primary is expected in February.