WASHINGTON — U.S. Sen. Cory Booker just visited 24 -- count 'em, 24 -- states stumping for Democrats in the midterm elections.

He contributed $686,000 to House and Senate candidates across the nation.

And along the way, New Jersey's dynamic Democrat stopped in all those early presidential primary states, plus a few that look to be big battlegrounds.

A dry run for a potential 2020 bid?

Even Booker wouldn't quarrel with that.

"I will consider running for president," Booker told NJ Advance Media.

"That's something that I will do. There's people in New Jersey who are talking to me about it, across the country that are talking to me about it, so I will consider that."

U.S. Sen. Cory Booker speaks at a get out the vote event at the University of New Hampshire in Durham on Oct. 28. (AP Photo | Cheryl Senter)

Booker said he spent the year focused on the midterms, which saw the Democrats win back the House, including capturing four of New Jersey's five Republican-held congressional districts.

Next on his agenda is trying to push legislation across the finish line during the lame-duck congressional session, including a bill to overhaul the criminal justice system that has President Donald Trump's support.

Then, he told NJ Advance Media, he will look at 2020, where he already has banked $4.1 million for his Senate re-election campaign. He figures that will come in earnest during the December holiday season.

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U.S. Sen. Cory Booker poses for a selfie with Dartmouth College students after addressing a gathering of college Democrats there. (Jonathan D. Salant | NJ Advance Media for NJ.com)

A recently enacted state law made it clear that he could seek both the presidency and another term in the Senate at the same time. And this time, a Democratic governor would appoint a successor if Booker reaches the White House.

"I know he's interested," said Rep. Bill Pascrell Jr., D-9th Dist.

"He's got a hell of a brand. I like his personality. He's got character. It's great that somebody from our own state would even think about it. I think he'll be listened to."

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U.S. Sen. Cory Booker prepares to snap a selfie after speaking in New Hampshire. (Jonathan D. Salant | NJ Advance Media for NJ.com)

He was listened to this fall.

Booker appeared with Jacky Rosen in Nevada and Kyrsten Sinema in Arizona, who wrested Senate seats away from Republicans, and with U.S. Sens. Sherrod Brown of Ohio and Tammy Baldwin of Wisconsin, both of whom won re-election in states carried by Donald Trump in 2016.

He drew standing-room-only crowds in New Hampshire, the first presidential primary state, and, after hearing him, hundreds of people signed up to work for the Democratic ticket.

He returned to the road just days before Thanksgiving, heading to Mississippi to campaign again for Democratic Senate candidate Mike Espy, who is in a runoff election with U.S. Sen. Cindy Hyde-Smith.

Espy is an underdog, but so was Doug Jones in Alabama, who Booker also campaigned for. Jones upset Roy Moore in December and became Alabama's first Democratic U.S. senator in more than two decades.

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"He's following the Obama playbook in '06," said Phil Singer, a veteran of the John Kerry and Hillary Clinton presidential campaigns. "He was able to parlay that into relationships. He was able to build up a favor bank."

New Hampshire Democrats were happy to have him in their state, where Booker paced in front of a large meeting room to urge voters to elect a Democratic governor and then squeezed into a storefront headquarters to tout a congressional candidate.

"It attracts volunteers," New Hampshire Democratic Party Chairman Ray Buckley said. "It attracts votes. It's the name of the game."

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Welcome to Mississippi, Senator! Glad you have the chance to meet with some of our best and brightest at @SouthernMiss. https://t.co/TudWmSS8ML — Mike Espy (@MikeEspyMS) November 19, 2018

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U.S. Sen. Cory Booker, left, listens as U.S. Sen. Robert Menendez speaks during a press conference in New Brunswick in September. (Patti Sapone | NJ Advance Media for NJ.com)

Back home in New Jersey, Booker helped carry U.S. Sen. Robert Menendez across the finish line in an unexpectedly competitive race, campaigning with him around the state.

"It's incredibly important, especially in a case like Cory where he has such a great standing with the people of New Jersey, well-regarded, and a validator of the work that I've done," said Menendez, D-N.J. "People will listen to someone independently of yourself."

Should he run, Booker's coast-to-coast campaigning will help prepare him for the rigors of a presidential race, Singer said.

"Just the stamina required to run for president, you need to train for it," Singer said. "Traveling around, refining and revising your stump speech, is a necessity for every aspiring candidate."

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U.S. Sen. Cory Booker chats with New Hampshire Democrats in Portsmouth. (Jonathan D. Salant | NJ Advance Media for NJ.com)

While not everyone Booker endorsed will return the favor in 2020 should he seek the presidency, some will. Booker also got to meet the party activists in the states he will need to do well in if he is to get the Democratic presidential nomination.

"We're an on-the-ground state," Portsmouth, N.H., Democratic Party Chair Laurie McCray said. "When we know our candidates well, when national figures come here, it's almost an affirmation of the work we do and the responsibility we have as the first- in-the-nation primary state."

While the Democratic field could be even larger than the 17 Republicans who sought for their party's nomination in 2016, GOP consultant Craig Stevens said that shouldn't dissuade Booker from running.

"If he ever wants to be president, he should at least go through the motions and see what the appetite is this cycle," said Stevens, who served as former Massachusetts Gov. Mitt Romney's 2008 New Hampshire communications director

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U.S. Sen. Cory Booker gestures while speaking before students at Dartmouth College.

So far, indications are that if Booker does run, he will start off as a top-tier candidate. Both the Washington Post and National Journal ranked him fifth among the potential Democratic candidates.

And US-Bookies, which aggregates European betting sites, put Booker third. His odds of winning the Democratic nomination were 10 to 1, behind only U.S. Sen. Kamala Harris, D-Calif., at 5 to 1; and Rep. Beto O'Rourke, D-Texas, at 6 to 1.

Should he not run for president, Booker still would come out ahead, thanks to his 2018 efforts, Singer said.

"At the very least, he did a good job winning chits with colleagues in the Senate, which will make him a more effective senator," Singer said. "It wasn't as if he wasted his time."

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U.S. Sen. Cory Booker discusses the cost of higher education before students at the University of New Hampshire.

On the campaign trail, Booker had several opportunities to test his popularity with younger voters, who tend to support Democratic candidates if they bother to go to the poll.

At age 49, Booker is a generation younger than three other potential 2020 presidential candidates, former Vice President Joe Biden and U.S. Sens. Bernie Sanders, I-Vt., and Elizabeth Warren, D-Mass.

No wonder his trip to New Hampshire last month was focused at college campuses. Young voters helped Obama in 2008 and Sanders in 2016.

"Cory probably plays right into that same crowd," said former Rep. Dick Swett, D-N.H. "He's young, he's exciting. That plays into what the young people are looking for."

When Booker went to Mississippi this month to campaign for Espy, he was booked to speak at the University of Southern Mississippi.

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Candidate signs form the backdrop as U.S. Sen. Cory Booker speaks at the University of New Hampshire. (Jonathan D. Salant | NJ Advance Media for NJ.com)

As for Booker's New Hampshire campaign swing, the Democratic gubernatorial nominee, Molly Kelly, fell short, even as the party took control of the state legislature.

But the congressional candidate who joined Booker in Portsmouth, Chris Pappas, won his race; and Rep. Annie Kuster, D-N.H., who appeared with the senator at Dartmouth College later in the day, was re-elected.

Booker will be the featured guest at a New Hampshire Democratic Party victory celebration next month.

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2020 Watch-NEW: Potential Democratic presidential contender @CoryBooker returns to NH on 12/8 for @NHDems 'Post Election Victory Celebration' in Manchester. The senator from NJ was was just in the #FITN presidential primary state in late October #nhpolitics #NJpolitics pic.twitter.com/ZCky68xGLw — Paul Steinhauser (@steinhauserNH1) November 19, 2018

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More on Booker in 2020

Booker for president? Murphy signs 'Cory Booker Law' that'll make it easier for him to run

Booker returning to New Hampshire in advance of big decision on 2020 presidential run

Cory Booker just wowed 'em in New Hampshire. Here's how he can do it again in a 2020 run for president.

Election 2018 is over. Here's where Cory Booker stands in newest 2020 presidential rankings.

I chased Cory Booker all over Iowa to see what Dems think of him. Their answers are fascinating.

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Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.