WASHINGTON — Facing an increasingly likely defeat in his tangled procedural fight over funding the government, Senator Ted Cruz took to the Senate floor on Tuesday and declared he would speak “until I cannot stand” to rally voters against the health care law.

While the Senate appeared ready to override him in a preliminary vote scheduled for Wednesday, Mr. Cruz, a freshman Republican from Texas, pressed ahead hour after hour with his opposition, comparing his fight to efforts by leaders who stood against the Nazis, ended the cold war or started the American Revolution.

“Everyone in America knows Obamacare is destroying the economy,” said Mr. Cruz, who began speaking at 2:41 p.m. and was still at it after 5 a.m.. “Where is the urgency?”

Yet outside the chamber, his colleagues worked against his efforts to block a vote to take up the House-passed bill that does precisely what he wants: financing the government through mid-December while cutting off money for the Affordable Care Act.