Updated Thursday

West Virginia Democratic Sen. Jay Rockefeller, one of the towering architects of Obamacare, on Tuesday openly criticized program managers for not moving quickly enough to build the system, warning that if it gets off to a bumpy start it will just get worse.

Decrying the Patient Protection and Affordable Care Act as way too complex, he warned the acting Medicare director that Obamacare is "so complicated and if it isn't done right the first time, it will just simply get worse."

The retiring senator also told Marilyn Tavenner at her Senate Finance Committee confirmation hearing to be administrator of the Centers for Medicare & Medicaid Services that Obamacare rivals tax reform in its capacity to confuse Americans.

"I believe that the Affordable Care Act is probably the most complex piece of legislation ever passed by the United States Congress. Tax reform obviously has been huge too, but up to this point it is just beyond comprehension," said Rockefeller.

Spokeswoman Abigail McDonough cautioned that Rockefeller remains an ardent supporter of Obamacare. She said, "Senator Rockefeller was a key author of the landmark health reform law and he is a very strong believer in the good that this law will do for so many millions of Americans. When the law is fully implemented in 2014, it will be the first time that such a sweeping health reform law goes into effect and there will undoubtedly be some challenges. But the Senator's point during Tuesday's hearing was to encourage the administration to get ahead of as many of those challenges as it can so that implementation goes as smoothly as possible."

Republican Sen. Richard Burr of North Carolina also hit Obamacare, questioning predictions that it will save money. He cited a recent analysis that insurers will face an average 30 percent increase in payouts for those covered by Obamacare, which could then be passed on to those insured outside of Obamacare.

But Tavenner suggested that other elements of Obamacare will "mitigate insurance increases," though she conceded that not all of the projected higher costs will be absorbed by those elements.

Despite the outcry over Obamacare, Tavenner received bipartisan praise and Obama officials said they expect her to win Senate confirmation, making her the first administrator of the Centers for Medicare & Medicaid Services since 2006. As a show of bipartisan support for the former Virginia top health official, she was introduced by House Majority Leader Eric Cantor and Sens. Tim Kaine and Mark Warner.

Another sign of her likely confirmation: During the last 20 minutes of the hearing for the woman who will oversee Obamacare, there wasn't a single Republican senator in the committee room.