* Marathon attack on Obama's signature achievement
* Cruz vows to speak as long as he can stand
* Must yield to Senate vote later in the day
By Thomas Ferraro and David Lawder
WASHINGTON, Sept 25 (Reuters) - U.S. Republican Senator Ted Cruz slogged into the second day of his marathon attack on Obamacare from the Senate floor on Wednesday, showing almost no signs of relenting after speaking for nearly 16 hours.
Standing in a nearly empty Senate chamber, Cruz made his case to deny funding to implement President Barack Obama's landmark overhaul of the U.S. healthcare system, calling it the country's "biggest jobs killer."
Most of the Tea Party firebrand's Republican colleagues shunned his diatribe against the health insurance reform law, which is delaying Senate consideration of a stop-gap funding measure needed to avoid a government shutdown in six days.
Elected from Texas last November, Cruz at times strides the Capitol attired in cowboy boots. But on Wednesday morning, his feet were clad in tennis shoes. In black, they matched his suit.
"Obamacare isn't working," the Texas Republican said in between stories about the struggles of his Cuban immigrant father and reciting Doctor Seuss verse. A professed carnivore, he recounted the tribulations of Christmas dinner with his future wife's vegetarian family.
Cruz began talking at 2:41 p.m. (1841 GMT) on Tuesday. His performance had the look of a filibuster, a procedural hurdle used to block legislation. Except in this case, it won't.
Under Senate rules, Cruz must yield the floor by noon (1600 GMT) on Wednesday for a procedural vote that will start the Senate towards final passage of the bill to keep government agencies funded through Nov. 15 -- including Obamacare money.
In the early hours of Wednesday morning, Cruz was joined on the Senate floor only by Republican Senator Mike Lee of Utah, who provided him short breaks from speaking. Lee and Cruz spent the summer whipping up conservative anger against the healthcare law.
As dawn approached, Sen. Marco Rubio of Florida, also a Tea Party conservative, took the lectern, giving a Cruz a break, which the Texas lawmaker used to stretch with knee bends on the Senate's floor.
Republicans agree with Cruz' contention that Obamacare is a "disaster," but most of the 46 Senate Republicans are expected to line up instead with their party leaders in support of the emergency spending bill.
Cruz wants to block the funding measure unless it contains no money to implement Obamacare.
Polls show most Americans oppose the health care law despite its goals of providing healthcare coverage to millions of uninsured people, but even more oppose a government shutdown.
Provided Cruz can remain on his feet, he could go on for several more hours until a procedural vote scheduled for midday on Wednesday.
"I intend to speak in support of defunding Obamacare until I am no longer able to stand," he said as he started his pitch.
Cruz went on to talk about his father "flippin' pancakes," making "green eggs and ham," "the travesty of Obamacare," and, proudly, about his unpopularity among many fellow Republicans. For more see
Practically every day, he said: "I now pick up the newspaper to learn what a scoundrel I am."
The Republican-controlled House of Representatives last week passed a version of the spending measure that denied funds to Obamacare. That will be stripped from the Senate version, which also will be shorter to
The House will have to decide whether to pass the revised bill or find a compromise with the Senate. Unless new funding is quickly approved, a government shutdown would begin on Tuesday.
At this point, it is unclear what the House Republican leadership would do, generating plenty of anxiety among their own members.
A House aide said of her boss: "He is definitely stressed."
The aide said the congressman opposes a shutdown but is under pressure from constituents to stop Obamacare.
Republicans uniformly want to repeal Obamacare. But many see that as a political impossibility as long as Democrats control the Senate and hold the presidency.
Club for Growth, a conservative group influential among Republicans, put senators on notice that it expected them to support Cruz's bid and block Democrats from eliminating the provision to defund Obamacare.
But Cruz's fellow Republicans were moving in the other direction one day after the party's top two leaders in the Senate, Mitch McConnell and John Cornyn, refused to lend their support to Cruz.
Senator Orrin Hatch, the senior Republican on the Finance Committee that oversees Obamacare, announced he would side with McConnell rather than Cruz.
Senator Lindsey Graham said he expects a majority of the Senate's Republicans to reject Cruz's strategy, which risks a government shutdown that would likely be blamed on Republicans.
"I think most Republicans believe, no matter how sincere you are about defunding Obamacare, that this approach would blow up in our face," Graham said.
Once the battle over the government funding bill is resolved, Congress will grapple with another fiscal crisis - a possible and unprecedented U.S. government default unless it agrees to raise the $16.7 trillion U.S. borrowing authority by sometime next month or early November.
Republicans are expected to place demands on any bill to increase the debt limit, including one to delay for a year implementation of Obamacare, now set to begin kicking in next month.