Sen. Jeff Merkley made his first stops in New Hampshire over the weekend, fanning speculation that he is considering a run for the Democratic presidential nomination in 2020.

The Oregon Democrat is in his second term and has built a résumé as one of the most progressive members of his caucus.

In New Hampshire, he discussed the “corrupting” effect of gerrymandering on U.S. politics, the Senate’s relationship with President Donald Trump, and how the conservative billionaire Koch brothers act as “puppet masters” over Republicans in the Senate.

Merkley predicted that Trump would not make it through his four-year term before stepping down or being removed from office.

“If I was gambling, I would gamble that he would not get through the term,” Merkley said in an interview with Manchester ABC affiliate WMUR, suggesting that the special counsel investigation into ties between Trump’s 2016 campaign and Russia would yield compromising information about the president. “The president is terrified of [Robert S.] Mueller looking into the transactions. He is terrified of the Russians.”

Merkley said his Republican colleagues in the Senate are “appalled” by Trump but are too afraid to publicly decry the president because they need his rabid base to stay in office.

“They are sticking by the president because the president’s 30 percent loyal base is a majority of their primaries,” he said. “It’s like inciting a mob to a lynching, and it’s very hard to stop the mob. And that’s how they view their base.”

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He also labeled the billionaire brothers Charles and David Koch “puppet masters” for many Republican senators, including members of leadership. 

Merkley was one of only eight Senate Democrats to vote against the omnibus spending bill Trump signed into law last Friday. He said he opposed the measure because it did not include a provision to address recipients of the Deferred Action for Childhood Arrivals program, also known as “Dreamers.”

“They are here,” he said. “They are contributing to our communities and to continue to use them as a political bargaining chip, as the president has, is a completely outrageous thing to do.”

Many saw the omnibus vote as a litmus test for potential Democratic presidential nominees in 2020. Sens. Cory Booker of New Jersey, Elizabeth Warren of Massachusetts, Kirsten Gillibrand of New York and Kamala Harris of California also voted against the bill.