Vermont Sen. Bernie Sanders fought President Barack Obama's proposed tax cut compromise with a lengthy speech in the Senate.
He started at 10:24 a.m. ET and ended at 7 p.m.
Sanders, 69, an independent who usually sides with Democrats, said it was unconscionable to increase the national debt "by giving tax breaks to millionaires and billionaires who don't need it."
Sanders noted he'd been repetitious in making his points.
He blasted Republican colleagues for their "hypocrisy" in wanting to extend tax cuts for the wealthy while complaining about the deficit.
He also read hardship letters from constituents struggling to pay heating bills.
"We should be embarrassed that we are for one second talking about a proposal that gives tax breaks to billionaires while we are ignoring the needs of working families, low income people and the middle class," he said.
Sen. Mary Landrieu, D-La., who also opposes the bill, briefly spelled him so he could take a break.
Despite the opposition, lawmakers expect the Senate to approve the bill early next week and send it to the House.
NBC News reported Sanders became a top trending topic on Twitter, under #filibernie, where some people repeated his quotes and others expressed amazement he was going on so long.
C-Span2 broadcast and livestreamed his talk.
"No matter what you believe, this guy is pretty awesome," tweeted renh77.
Sanders lengthy talk was not a true filibuster, as NBC reported, as he was not holding up any Senate business and no votes or other speeches were scheduled.
According to the Associated Press, the last true filibuster was mounted in 1992, when then- Sen. Al D'Amato, R-N.Y., spoke for for 15 hours and 14 minutes to oppose a change in a tax bill that would have hurt a home-state typewriter company.
Sanders, too, tweeted on his @senatorsanders account: "You can call what i am doing today whatever you want, you it call it a filibuster, you can call it a very long speech..."
He also tweeted his wrap-up: "And with that, Madam President, I would yield the floor."