U.S. Sen. Jeff Merkley today became the first U.S. Senator to endorse Democratic presidential candidate Bernie Sanders.

“After considering the biggest challenges facing our nation and the future I want for my children and our country, I have decided to become the first member of the Senate to support my colleague Bernie Sanders for president,” the Senator from Oregon wrote in an editorial for The New York Times.

Merkley contends that President Obama has made the country “fairer and more prosperous for all” and Hillary Clinton would be “a strong and capable president.

“But Bernie Sanders is boldly and fiercely addressing the biggest challenges facing our country,” he wrote.

Merkley cited Sanders’ positions on trade deals, fossil fuels, campaign contributions, predatory lending, and other issues for earning his support.

“It has been noted that Bernie has an uphill battle ahead of him to win the Democratic nomination,” he said. “But his leadership on these issues and his willingness to fearlessly stand up to the powers that be have galvanized a grass-roots movement.”

Oregon Live notes that Merkley’s endorsement comes as his home state prepares to send out vote by mail ballots.

“This is just the right time for Oregon,” Merkley told MSNBC’s “The Morning Joe.” “Oregon has a vote by mail. The ballots get mailed out on the 28^th of this month, and so …”

Merkley told the hosts he thinks Sanders has a real shot at the White House.

“I think anything is possible in a campaign,” he said. “Obviously, the math is an uphill climb, but we’ve been surprised by what happens in campaigns time and time again.”

Merkley also explained why he decided to become the first Senator to get behind Sanders.

“Because this really is all about the person who has the boldest, most fierce vision on the biggest issues facing America and the world,” he told MSNBC. “Certainly that’s true in terms of international trade. Bernie understands that these trade treaties where we compete with people earning as little as a dollar an hour have done enormous damage to the leverage of American workers, have shipped a tremendous number of jobs overseas.

“He’s fought for healthcare, the expansion of the federally qualified health centers was really his baby …,” Merkley said, adding that Bernie is the best to deal with “global warming,” as well.

The Senator was questioned about Sanders’ alleged hesitation during “tough questions” about his proposals during an interview with the New York Daily News’ editorial board, which the paper later used to justify its endorsement of Hillary Clinton.

“Certainly, you have got to judge someone by the totality of their record,” Merkley said. “And he’s put forward a number of detailed proposals. He backed the Volcker Rule, which took the gambling out of Wall Street. He backed the amendment to cap the share of deposits that any single big bank could have. He backed the increased levels of capital required if you’re a significant financial institution.”