Hillary Clinton's running mate, Sen. Tim Kaine, is shaking off the presidential ticket's stinging defeat and promising to serve as an "emergency break" for Donald Trump's agenda in the Senate.

"The most important role I have is here in the Senate because the Democratic Senate minority is about the only emergency break there is on the train right now," Kaine told reporters on his first day back in the Senate since he and Hillary Clinton's White House went down in a decisive defeat.

The Senate's Democratic minority he said, still maintains the ability to "shine a bright spotlight, sometimes slow things down and sometimes stop things, if they need to be stopped," the Virginia senator said.

"Advance everywhere you can and defend everything you must — that's my motto," Kaine added.

Asked whether he would use that "emergency break" to block Trump's Supreme Court nominees, Kaine said he would not preemptively react to a choice before it is made.

He is clearly not pleased with one of the first Trump appointments, the elevation of former Breitbart News CEO Steve Bannon to chief strategist.

"I feel that putting someone into that chief advisory role who has a history of connections to white nationalists and anti-Semitism is very troubling," he said.

Kaine also readily reflected on his rollercoaster experience of running for vice president, and the highs and lows of the most unconventional presidential campaign in modern history.

"I'm proud that we did so well in Virginia," he said, a state where Clinton squeaked out a victory. "I'm proud for Hillary because she won the popular vote and there's history there … and I'm glad that I've got work to do here" in the Senate.

After such a frenetic race and unexpected Trump victory, the Virginia Democrat said he's coming back to the Senate "a little sadder, a little wiser and a lot energized."

In some ways, Kaine said he is breathing a sigh of relief that he can continue his life's work as a senator without a constant Secret Service entourage and the spotlight and scrutiny that comes with serving as a vice president.

He described the feeling as similar to when he left the Virginia governorship when his term was over.

"You have the inauguration and [the Secret Service] drops you off, and they drive away, and I had the same feeling this time," he said, noting that shaking hands with everyone on the Clinton campaign team was very "emotional."

"Watching the [Secret Service] cars drive away, I had an immense feeling of relief because I have a life where I do work that I feel is important but everybody in Richmond is so used to me, I'm just a regular person. I can go to the dry cleaners and hang out and go to the coffee shop, and people say, 'Hey, Tim, what's up?' and people are used to me."

"That's what I like," he added. "The entourage was cool on occasion, but it was never me."