Sen. Jeff MerkleyJeffrey (Jeff) Alan MerkleyInterest rate caps are popular — for good reason Overnight Energy: EPA to regulate 'forever chemicals' in drinking water | Trump budget calls for slashing funds for climate science centers | House Dems urge banks not to fund drilling in Arctic refuge Democratic senators criticize plan that could expand Arctic oil and gas development MORE (D-Ore.) in a New York Times op-ed published early Wednesday became the first senator to back Bernie SandersBernie SandersDNC warns campaigns about cybersecurity after attempted scam Overnight Health Care — Presented by American Health Care Association — Trump taps Pence to lead coronavirus response | Trump accuses Pelosi of trying to create panic | CDC confirms case of 'unknown' origin | Schumer wants .5 billion in emergency funds Biden looks to shore up lead in S.C. MORE’s presidential campaign.

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Merkley said he’s supporting his Senate colleague over front-runner Hillary ClintonHillary Diane Rodham ClintonDNC warns campaigns about cybersecurity after attempted scam Biden looks to shore up lead in S.C. Stone judge under pressure over calls for new trial MORE because Sanders “is boldly and fiercely addressing the biggest challenges facing our country.”

“It is time to recommit ourselves to that vision of a country that measures our nation’s success not at the boardroom table, but at kitchen tables across America,” Merkley wrote. “Bernie Sanders stands for that America, and so I stand with Bernie Sanders for president.”

The Oregon Democrat pointed to Sanders’s positions on trade deals, fossil fuels and renewable energy, campaign financing and predatory lending.

Sanders has been hitting those issues ahead of next week's primary in New York, where Clinton is aiming to blunt Sanders's winning streak. She maintains a large delegate lead.

Merkley said Clinton would be a “strong and capable” president, citing her “remarkable record.”

The Oregon lawmaker is among the last senators to endorse in the Democratic race.

Democratic Sens. Jon TesterJonathan (Jon) TesterDemocratic senator: 'The ultimate of ironies' for Trump to hit Romney for invoking his faith Committee on Veterans Affairs sends important message during tense Senate time Democrats cry foul over Schiff backlash MORE (Mont.), Elizabeth WarrenElizabeth Ann WarrenBiden looks to shore up lead in S.C. Hillicon Valley: Dems cancel surveillance vote after pushback to amendments | Facebook to ban certain coronavirus ads | Lawmakers grill online ticketing execs | Hacker accessed facial recognition company's database Push for national popular vote movement gets boost from conservatives MORE (Mass.) and Robert MenendezRobert (Bob) MenendezMenendez calls for 'Marie Yovanovitch bill' to protect foreign service employees Senators condemn UN 'blacklisting' of US companies in Israeli settlements Media's selective outrage exposed in McSally-Raju kerfuffle MORE (N.J.) have not backed any candidate. Sen. Angus KingAngus KingOcasio-Cortez defends Sanders running as a Democrat: It's 'more than what you call yourself' Use of voting tabulation apps raise red flags on Capitol Hill Patrick Dempsey to star in pilot for CBS political drama 'Ways and Means' MORE (I-Maine) has yet to endorse anyone, as well.

"This is just the right time for Oregon," Merkley said on MSNBC's "Morning Joe" while discussing the timing of his endorsement, noting mail ballots in Oregon will go out later this month.

Asked if he thought Sanders could win, Merkley responded, "I think that anything is possible in a campaign."  

"Obviously the math is an uphill climb," he added.

Jesse Byrnes contributed to this report, which was updated at 7:27 a.m.