Retiring Sen. Tom Harkin, D-Iowa, said Obamacare is "in a good place" for implementation moving forward, adding that his colleagues should campaign on the law even if he isn't.

"Have we made mistakes? Yeah, we've made some mistakes, sure we have, and maybe [there are] some things we should have done a little bit differently," Harkin, who leads the Senate Health, Education, Labor and Pensions Committee, told C-SPAN while responding to a question about Democratic messaging on the bill.

"But, these are the kinds of mistakes you make when you are making big changes in something as personal to people as their health care insurance."

A new poll shows that 56 percent of Americans have an unfavorable view of the health care law. "One in three U.S. voters now says his or her health insurance coverage has changed as a result of Obamacare, and the same number say the new national health care law had a negative personal impact on them," according to Rasmussen Reports.

Should Democrats campaign on the law in 2014? "Absolutely," Harkin said, arguing that Americans who have signed up for the law will not support politicians who push for its repeal. "Of course, I'm not running for re-election."

A Harper Polling/Conservative Intel survey taken in November found that Obamacare has terrible numbers in Harkin's state. "The poll finds that likely Iowa voters disapprove of Obamacare, 54 to 34 percent, and that 52 percent say they are more likely to vote for an Obamacare opponent, versus 39 percent who say they are more likely to vote for an Obamacare supporter," David Freddoso wrote.