Sen. Jeff MerkleyJeff MerkleyOPINION | Shailene Woodley: US should run on renewable energy by 2050 Gore wishes Mikulski a happy birthday at 'Inconvenient Sequel' premiere Callista Gingrich touts Trump's commitment to environment despite Paris deal pullout MORE (D-Ore.) held an all-night talkathon from the Senate floor to protest Neil Gorsuch's Supreme Court nomination.

The Oregon Democrat started speaking shortly before 7 p.m. Tuesday and was still speaking as of 7 a.m. on Wednesday morning, more than 12 hours later.

He is expected to "hold the floor and refuse to yield for as long as he is able to continue speaking," according to his office.

"It's my understanding that the sun is coming up behind the Supreme Court. I was struck by how beautiful the weather was yesterday while the weather inside this building was so dark and gloomy," Merkley said just after 6 a.m. "Partisan politics gave us a very, very ugly setting here."

Merkley is using his hourslong speech to lay out broad criticisms of the current Supreme Court fight, including arguing that Republicans "stole" the seat and are "court packing."

“How about we save the integrity of the Senate?" he asked from the Senate floor. "How about we save the integrity of the Supreme Court?”

Sen. Dick DurbinDick DurbinMcCain rivals praise senator after brain cancer diagnosis Graham and Kushner met to discuss immigration differences: report Trump's FBI nominee passes committee, heads to full Senate MORE (D-Ill.) became the first senator to join Merkley's talkathon, coming to the floor around 6:30 a.m. and running through a litany of concerns about Gorsuch and the GOP strategy

"This is part of a concerted effort by Republicans to take control of the federal judiciary," the No. 2 Democrat said.

Durbin also suggested that GOP groups are spending millions to help confirm Gorsuch because they think he will "rule along the lines that they believe."

Merkley, who is a member of Democratic leadership, blasted Senate Republicans on Tuesday night, accusing of them trying to choke off debate over Gorsuch's nomination.

“Here we are in the first day, just hours into debate, and the majority leader said, 'Enough. We don’t want to hear any more about this topic. We’re going to shut down debate,'" Merkley said, referring to Senate Majority Leader Mitch McConnellMitch McConnellSenators, you passed ObamaCare repeal-only bill in 2015 — do it again Senate heads to new healthcare vote with no clear plan McCain absence adds to GOP agenda’s uncertainty MORE's (R-Ky.) decision to file cloture earlier Tuesday.

He added that senators should slow down and "recapture the type of cooperation and bipartisanship that made this chamber able to address the problems facing America."

His marathon speech isn't expected to impact the Senate's consideration of Trump's nominee, with an initial vote set to take place Thursday morning.

The liberal senator has been a vocal opponent of Gorsuch's nomination, predicting as early as late January that his party would filibuster Trump's pick.

He argued on Tuesday night that by refusing to give a hearing or vote for Merrick Garland, former President Obama's nominee, Republicans are now trying to fill a "stolen seat."

"Wouldn't it have been incredible if President Trump's nominee ... had stood up and said 'I will not participate in this crime against the Constitution' and declined the nomination?" Merkley asked from the Senate floor.

Merkley's speech comes as the Senate formally kicked off debate on Gorsuch's nomination on Tuesday.

Democrats are largely opposed to Gorsuch's nomination. Only four Democrats have said they will help Trump's pick get over an initial procedural hurdle.

Merkley's colleagues as well as liberal outside groups offered him support for his all-night speech.

Senate Minority Leader Charles SchumerCharles SchumerLawmakers send McCain well wishes after cancer diagnosis OPINION | GOP's 7-year ObamaCare blood oath ends in failure Dems tout failure of GOP healthcare bill MORE (D-N.Y.) gave him a shoutout on social media, saying his floor speech is "what we're all watching tonight."

Merkley — reiterating a frequent liberal talking point — added that the Senate shouldn't confirm a Trump Supreme Court nominee amid an FBI investigation into Russia's meddling in the White House race and any ties between Trump officials and Moscow.

“This is a very serious question. There is a very dark loud over the legitimacy of the election, and therefore, the legitimacy of the president," he said.

He added any ties between Trump campaign officials and Russia would be "traitorous."

As Merkley's speech entered its fifth hour, he also knocked Trump over a myriad of other policies, including his plan to build a U.S.-Mexico border wall and breaking his pledge to "drain the swamp" by setting up a "swamp Cabinet."

"The point that border experts made is that the wall will be useless in stopping drugs from entering our country," he said.

In an email sent out Tuesday night, Merkley's campaign team said that his speech was aimed at pressuring GOP leadership "to pull Gorsuch's nomination."

Merkley wants Senate Republicans to back renominating Garland or someone in his mold.

"If you don't have the votes, change the nominee, not the rule," he said.

There is no sign that Republicans will reverse course on Gorsuch.

With 44 senators opposing Gorsuch's nomination, Senate Republicans are expected to vote on Thursday to change the Senate's rules so he can be confirmed by a simple majority.

Republicans quickly pounced on Merkley's talkathon, chalking it up to a 11th hour effort that is doomed to fail.

Nathan Brand, a spokesman for the conservative America Rising Squared, compared his speech to "those all-nighters before a test in college."

"While Senator Merkley's desperate floor speech may serve him well with his looney liberal base, it also shows how Senate Democrats have been co-opted by the extreme activists in their party," he said.

This report was updated on April 5 at 7:24 a.m.