Welcome to Health Reform Watch, Sarah Kliff’s regular look at how the Affordable Care Act is changing the American health-care system — and being changed by it. You can reach Sarah with questions, comments and suggestions here. Check back every Monday, Wednesday and Friday afternoon for the latest edition, and read previous columns here.

(REUTERS/Jessica Rinaldi)

Months before the law's main components roll out, Republicans are reviving their campaign against Obamacare. Among health law supporters and journalists, the question now is: Why isn't the Obama administration doing more to fight back?

"I don't see any possible response to the Republican attacks except for Democrats except to get out of their crouch and start selling Obamacare like their lives depended on it," Kevin Drum wrote in Mother Jones on Tuesday. "A moderate response just won't do any good here."

Jill Lawrence at the National Journal said the same about a month ago, right when the health law hit its third anniversary but still wasn't gaining in popularity.

"They've got to uncurb their enthusiasm," Lawrence wrote of Obamacare supporters, "and keep it out front for months if they want the public to warm to this law and the people who made it happen."

The law includes a lot of provisions that actually are popular, such as ending the practice of turning down applicants for preexisting conditions and subsidizing health insurance coverage. Why doesn't the administration have an ad campaign celebrating those?

I've put this question to top administration officials and advocates, and the answer tends to be this: If we start selling Obamacare now, we're going to be raving about a product that doesn't yet exist. That would, in turn, undermine the sales pitch they want to make in October, when enrollment in the new health plans opens.

"We've done a lot of research on that," Medicare administrator Marilyn Tavenner said when I asked about the outreach strategy. "Our research has shown if you go too early, you don’t have anything to offer, and people lose interest. It will be intense, but the timing is important."

Enroll America, a new nonprofit that will focus on Obamacare outreach, has also considered the timing of a public information blitz.

"We do have to be mindful about how we talk about the law before October 1, when folks can actually go online and sign up in the exchanges," executive director Anne Filipic said recently. "We’ll have a strong presence before the exchanges, definitely, but we have to be smart about what that looks like."

Both Enroll America and the Obama administration have discussed early summer, around June or so, as the point at which they'll start ramping up their outreach campaigns. That's when they believe they can start talking about health benefits that will become accessible a few months down the road.

So, as Republican take more shots at the health care law, the Obama administration's relative silence is part of a larger plan.

KLIFF NOTES: Top health policy reads from around the Web.

ICYMI: Medicare just made a whole bunch of hospital prices public. "For the first time, the federal government will release the prices that hospitals charge for the 100 most common inpatient procedures. Until now, these charges have been closely held by facilities that see a competitive advantage in shielding their fees from competitors. What the numbers reveal is a health-care system with tremendous, seemingly random variation in the costs of services." Sarah Kliff and Dan Keating in The Washington Post.

Sen. Harkin has lifted his hold on Marilyn Tavenner's nomination to become Medicare administrator. "Sen. Tom Harkin Tuesday removed the hold he had placed on the nomination of Marilyn Tavenner to head the Centers for Medicare and Medicaid Services and said he would no longer stand in the way of a Senate vote despite actions by the Obama administration that he said violate “both the letter and the spirit” of the 2010 health care law." Mary Agnes Carey in Kaiser Health News.

The slowdown in health costs may be here to stay. "Major new studies from researchers at Harvard University, the Henry J. Kaiser Family Foundation and elsewhere have concurred that at least some of the slowdown is unrelated to the recession, and might persist as the economy recovers. David M. Cutler, the Harvard health economist and former Obama adviser, estimates that, given the dynamics of the slowdown, economists might be overestimating public health spending over the next decade by as much as $770 billion." Annie Lowrey in the New York Times.