Avik Roy has the scoop. The mandate was never popular, so one naturally senses politics being behind this decision. As Roy notes, the mandate might have driven up unemployment, so delaying it for a year might keep unemployment from becoming even more of an issue during the 2014 midterm election cycle. Additionally, as Roy points out, delaying the mandate will cause more people to want to enroll in the individual insurance exchanges set up by the Affordable Care Act. The following from Roy's post is also notable:

The Affordable Care Act is quite clear as to the effective date of the employer mandate. “The amendments made by this section shall apply to months beginning after December 31, 2013,” concludes Section 1513.

The executive branch is charged with enforcing the law, and it can of course choose not to enforce the law if it wants. But people can sue the federal government, and a judge could theoretically force the administration to enforce the mandate.

So the question is: Would anyone sue the Obama administration over this? Employers, of course, will be thrilled to be spared the mandate for one more year. Democratic politicians, similarly, will be glad to have this not hanging over their heads for the 2014 mid-term election.

The wild-card is left-wing activists. Most, you’d think, would defer to the administration on questions of implementation. I’m no lawyer, but it seems to me that all it would take is for one judge to issue an injunction, for an activist to require the administration to enforce the mandate.