Door-knocking. Expensive television ads. Independent groups lining up in support. President Obama's third political campaign — this time, to make Obamacare a success — looks like his first two. But it isn't going quite as well.

The New York Times spent a day trailing canvassers in Florida, hired by independent groups to knock on doors and encourage people to sign up for insurance. The trick is that, unlike a political campaign, consultants have to guess who does or doesn't have insurance, ranking people on a 1 to 100 scale for the likelihood that they need coverage. (In a political campaign, voter registration data and vote history are easy to ascertain.) That guesswork leads to scenes like this one:

Many of their targets, people identified on sophisticated computer lists generated in Washington as unlikely to have health insurance, had moved away. Some were not home. Many said they already had insurance through Medicare, their parents or a job. A few were hostile at the mere mention of President Obama’s health care law.

“We’re going to repeal that,” one man said gruffly as he shut the door in the face of a canvasser, Nancy Morwin, 58, a retired social worker.

The Times says that canvassers, hired by Planned Parenthood or a group called Enroll America, are knocking on tens of thousands of doors and employing thousands of workers to get people enrolled. At the same time, the White House is leveraging its Hollywood relationships to get celebrities tweeting and speaking out about enrolling. (Enroll America is the group behind the "Pets for Obamacare" spot from a few weeks ago.) State exchanges are using a slew of similar tricks, part of a heavy push to get people to sign up. Not a big factor, apparently: Organizing For Action, the group that is a direct offshoot of the Obama 2012 campaign apparatus. 

New enrollments in the Obamacare exchanges are critical to the success of the bill, which counts on keeping costs low by getting relatively healthy people to sign up for plans thanks to the mandate that individuals have coverage. If not enough people enroll or if people whose medical needs are too expensive enroll heavily, the economics of the system break down.

The Wall Street Journal sorts through some of the competing concerns as the critical March 30 date approaches. (That date is three months into the year; if people aren't covered with insurance for at least nine months of 2014, the individual mandate penalty applies.) The Journal samples one from each group of "voters" in this campaign: people without insurance who strongly support Obamacare, people who are seeing their policy costs increase to meet new Obamacare requirements (and who are less excited), businesses trying to figure out how to handle new requirements and, in some cases, costs. There's a not-coincidental overlap between those groups and the constituencies that lined up behind Obama and Romney in 2012.

To be fair, what the Times outlines as challenges in the grass-roots enrollment process will seem familiar to anyone who has ever done canvassing work in a campaign. People aren't home. People don't want to answer the door. People are skeptical. Your data is bad. It's part and parcel of the work, and not a strong indicator that enrollment efforts will come up short.

Nor should Obamacare advocates worry too much about the other opposition tactic at play: Legislative tweaks to Obamacare. To extend the campaign analogy, Congressional Republican efforts to rescind the law or change parts of it are like filing election complaints against a candidate, except that, in this case, it's the competing candidate that gets to rule on them. Louisiana Rep. Steve Scalise introduced a bill that would delay the individual mandate until 2016. That would serve two needs: making the issue central to the 2016 presidential race and pushing the mandate (and its burst of higher-profit enrollments) out to the end of the period covered under the "risk corridors," in which insurers are offered some protections in case the economics of enrollments aren't working out. But that bill would eventually need to be signed by Obama, if it even got to him, and Obama would obviously say no.

This campaign won't end on a technicality. Instead, it's going to be a grueling, multi-year push to gauge support and encourage people to vote on behalf of the president's legacy. The polling numbers are measured in enrollments (still behind targets) and on the balance sheets of insurance companies. That's what must be making Obama nervous. For the first time in his three campaigns, he's trailing.