Egged on by conservative groups, the potential 2016 presidential candidate excoriated Republicans and Democrats in his criticism of Obama's signature domestic achievement and Congress' unwillingness to gut the law. Cruz supports the House-passed bill that would avert a government shutdown and defund Obamacare, as do many Republicans.
However, they lack the votes to stop Senate Majority Leader Harry Reid, D-Nev., from moving ahead on the measure, stripping the health care provision and sending the spending bill back to the House.
That didn't stop Cruz' quixotic filibuster. During his talkathon, eight Republicans joined Cruz on the Senate floor, including Sen. Rand Paul of Kentucky and Sen. Marco Rubio of Florida, both of whom have been mentioned as possible presidential candidates. Cruz yielded to them for questions but did not give up his time controlling the debate.
"It is my hope, my fervent hope, that the voices of dissension within the Republican conference will stop firing at each other and start firing" at the target of the health care law, said Cruz in a clear acknowledgment of GOP opposition.
Senate Minority Leader Mitch McConnell, R-Ky., and the GOP's No. 2, Sen. John Cornyn of Texas, opposed Cruz' tactic, and numerous Republicans stood with their leadership rather than Cruz. Sen. John Thune, the third-ranking Republican, declined to state his position.
"I think we'd all be hard-pressed to explain why we were opposed to a bill that we're in favor of," McConnell told reporters. "And invoking cloture on a bill that defunds Obamacare, it doesn't raise taxes, and respects the Budget Control Act strikes me as a no brainer."
McConnell told rank-and-file senators privately and reporters publicly that the GOP should not speak as long as the rules permit on the legislation, for fear it would give them little time to try to turn the political tables on Democrats or to avoid a possible shutdown.
Delaying tactics could push a final vote into the weekend, just days before the new fiscal year begins on Oct. 1. That would give Speaker John Boehner, R-Ohio, and House Republicans little time to come up with a new bill.
McConnell told reporters that if the House doesn't get a Senate-passed bill until Monday, lawmakers there would be in a tough spot.
"Delaying the opportunity for the House to send something back, it seems, plays right into the hands of Senate Democrats," Sen. Bob Corker, R-Tenn., said. "If I'm Harry (Reid), what I'd hope would happen is you wait until the very last minute to send something over to the House."
Asked whether there were any efforts in the GOP meeting to persuade Cruz and Lee to speed up Senate debate, Corker said, "The discussion came up about the advantage of having House Republicans weigh in again. And there were two senators who did not like that idea, not to name who they are."
The bill would keep the government operating until Dec. 15 and gut Obamacare.
Sen. Dick Durbin, the Senate's No. 2 Democrat, said Democrats favor a spending bill that would keep the government running until Nov. 15, which would force Congress to work sooner on a more sweeping piece of legislation known as an omnibus spending bill that he hopes would reverse some automatic spending cuts known as sequestration.
Despite Cruz' effort, a test vote was set for Wednesday. Reid had filed a motion to proceed to the measure, and under Senate rules lawmakers will vote even if Cruz speaks for hours and keeps the Senate in session overnight.
In one exchange late Tuesday, Durbin mentioned that the Princeton and Harvard-educated Cruz had gone to "some very famous schools," and then pressed the Texan on the fact that the numbers simply don't add up for him to prevail.
Cruz said he wasn't delusional and insisted that his move was the first of many steps to unravel the law.
In another exchange, Sen. Tim Kaine, D-Va., pointed to Obama's re-election as the electorate's word on the health care law. Cruz said Obama was a "far more talented candidate" than Mitt Romney and didn't see the 2012 election as a referendum on the health care law.
The Cruz filibuster echoed the effort of Paul, who in March waged a nearly 13-hour filibuster of John Brennan's nomination for CIA director over the president's authority to use drones in the United States. The Senate eventually confirmed Brennan.
Outside conservative groups that have been targeting Republican incumbents implored their members to call lawmakers and demand that they stand with Cruz and his attack on Obamacare.
"This is the ultimate betrayal," the Senate Conservatives Fund said of McConnell and Cornyn two lawmakers up for re-election next year in an email Tuesday morning. They pressed their members to "melt the phones," arguing that "we can't let these turncoats force millions of Americans into this liberal train wreck."
The Club for Growth and the Madison Project also pressed lawmakers to back Cruz' effort.
The issue has roiled the Republican Party, exacerbating the divide between tea party conservatives and GOP incumbents who repeatedly have voted against the health care law but now find themselves on the defensive. Republican senators said defunding Obamacare simply won't happen with a Democratic president and Democrats controlling the Senate.
"It will be a cold day in Gila Bend, Ariz., before we defund Obamacare," said Sen. John McCain, R-Ariz., the party's 2008 presidential nominee. "A very cold day. In fact there may be a snowstorm. ... I know how this movie ends. I don't know all the scenes before it ends, but I know how it ends. We don't defund Obamacare."
Associated Press writers Andrew Taylor, Alan Fram, David Espo and Laurie Kellman contributed to this report.