As dawn broke over Washington Wednesday morning, Sen. Ted Cruz still held the Senate floor, 16 hours into a filibuster designed to draw attention to the GOP’s effort to defund Obamacare — and topping the length of Sen. Rand Paul’s filibuster earlier this year.

“As difficult as it is to cross one’s party leaders, I say — with perhaps a little familiarity to the consequences — that it’s survivable, and ultimately it’s liberating,” Mr. Cruz said in the early morning hours of his talk-a-thon, which he began at 2:41 p.m. Tuesday afternoon and showed little fatigue at 5:40 the next morning.

Over night he read excerpts from both Ayn Rand’s “Atlas Shrugged” and from Dr. Seuss’ “Green Eggs and Ham” on the floor, cited approvingly the words of wisdom from actor Ashton Kutcher and hit TV show “Duck Dynasty,” carefully sipped water, and grabbed a quick snack at one point while fellow filibuster leader Sen. Mike Lee asked a 45-minute-long question, giving the Texas Republican a chance to stretch his legs, check messages on his iPhone and confer with his staff.

As 7 a.m. dawned, Mr. Cruz was still on the floor and, prompted by a question from Sen. Marco Rubio, he pondered whether the appropriate comparison for the health care law was the “Friday the 13th” movie series protagonist Jason, or the “Nightmare on Elm Street” movie franchise anti-hero Freddy.

“You can make a powerful argument for Jason because Obamacare is the biggest job-killer in this nation,” Mr. Cruz said. “But on the other hand, you could make a powerful argument for Freddy because, as James Hoffa said, president of the Teamsters, Obamacare is a nightmare.”

Mr. Cruz had vowed to keep talking until he couldn’t stand any longer.