U.S. Senator Jeff Merkley, who has competed in Ironman triathlons, launched a different kind of endurance event yesterday.

Oregon's junior Senator filibustered Supreme Court nominee Neil Gorsuch for 15 hours on the Senate floor before finally yielding just after 10 a.m. Eastern Standard Time this morning.

"Make no mistake: This is a stolen seat -- & if this theft is completed, it will undermine the integrity of the court for decades," Merkley tweeted as he took to the Senate floor yesterday shortly before 7 p.m.

The Gorsuch nomination and the election of President Trump has helped raise partisan rancor in Washington DC to new heights. Many Democrats are still seething over Republicans' refusal last year to even vote on former President Barack Obama's nomination of Merrick Garland to the court. Now, the tables are turned and Democrats have sufficient votes to block Gorsuch.

Merkley took the floor yesterday evening immediately after it became clear that Senate Pres. Mitch McConnell was moving to end debate on the nomination.

Why he did so is not entirely clear. The main Democratic fillibuster is expected to begin Thursday.

Filllibusters are a time-honored tactic in Congress. They are viewed as an important procedural check on the power of the party in control, which can end a fillibuster only if it can muster 60 votes. In the case of Gorsuch, McConnell doesn't have the votes.

But McConnell is threatening the so-called "nuclear option" -- changing the rules so that Republicans could end fillibusters with a simple majority vote.

Ironically, Democrats, including Merkley, have in past years threatened the nuclear option when their candidates were blocked by Republicans.

Merkley's lead role in the fight against Gorsuch will burnish his reputation as one of the leading progressives in the Senate. He made it clear in an interview last week that he would go to great lengths to block Gorsuch, who he views as a tool of wealthy special interests.

"Dark money" has become one of the great issues of the moment in Washington DC. Wealthy activist billionaires, who often happen to be conservative, have reshaped national politics throwing their money behind candidates and causes.

Sen. Sheldon Whitehouse, D-Rhode Island, challenged Gorsuch to identify who was bankrolling the estimated $10 million PR campaign supporting his nomination. Gorsuch declined. "It is what is it is," Gorsuch said. "If you want to require disclosure, pass a law."

"Dark money is completely corrupting the institutions of America, it's dark money backing Gorsuch," Merkley said.

-- Jeff Manning

503-294-7606, jmanning@oregonian.com