Former New Hampshire US senator Gordon Humphrey said he would vote for Clinton largely because of his feelings about Republican presidential candidate Donald Trump.

Democratic presidential candidate Hillary Clinton picked up the vote of one New Hampshire’s more outspoken arch-conservatives on Sunday.

“On Tuesday, millions of lifelong Republicans will vote against Donald Trump. I’m one of them,” Humphrey said in a Clinton campaign video released Sunday afternoon. “For the sake of our families’ safety, let’s stand together against Donald Trump by voting for Hillary Clinton. It’s the responsible thing to do.”

The idea that Humphrey would back a Democratic presidential candidate is a stunning development in New Hampshire politics. During his time in the US Senate from 1978 to 1990 and his two runs for governor after returning from Washington, he has been ruthless in his criticism of Democrats.


He has also not recently faded away from the Republican Party. He was a major backer of Tea Party efforts in the state a few years ago and attended the Republican National Convention in July as a John Kasich delegate.

However, all year he has been a chief Republican Trump critic. At the party’s national convention he was a leader of an effort that would have made it harder procedurally for Trump to become the nominee.

While Humphrey has walked away from Trump, the man who replaced him in the US Senate, former senator Bob Smith, is enthusiastically endorsing Trump and has spoken at many recent Trump rallies in the state.

“I am going to assume now that Senator Humphrey is not going to get a position in the Trump administration now,” Smith joked when informed of the news. “I am disappointed.”

Of course, Smith, too, knows a thing or two about the endorsing a Democrat for president. In 2004, he endorsed John Kerry over then-President George W. Bush.


The 2016 election

Gordon Humphrey, shown at the Republican National Convention in Cleveland, was a leader in the "Never Trump" movement. Mark Kauzlarich/Reuters/File

James Pindell can be reached at james.pindell@globe.com. Follow him on Twitter @jamespindell. Click here to subscribe to his daily e-mail update on the 2016 campaign.