But this window of opportunity closes quickly. After 16 months, the midterm elections loom, and Congress tends to freeze.
Second, presidents can take strong action throughout their time in office when they are able to obtain broad grants of authority. After the Sept. 11 attacks, for example, the George W. Bush administration asked for and received the power "to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons." For the rest of his presidency, the Authorization for the Use of Military Force enabled President Bush to do most of what he sought to do.
In a similar fashion, important provisions of the Clean Air Act allow the Environmental Protection Agency to issue national air-quality standards that are "requisite to protect the public health." The Obama administration has used phrases of this sort to control a number of air pollutants, including greenhouse gases. Whenever a president seeks new legislation, it is in his or her interest to seek authority of this kind. (Whether such authority is always in the interest of the nation is another question.)
Finally, under creatively designed laws, significant reform can happen as a result of congressional inaction. Consider, for example, the Defense Base Realignment and Closure Act of 1990, which enables the president to appoint the nine members of a base-closing commission. The commission produces a list of recommended military-base closures, and if the president approves, they happen - unless Congress enacts a resolution of disapproval within 45 days. If Congress does nothing, the closures go into effect.
A more controversial example is the sequester. In 2011, Congress and President Barack Obama completed a difficult negotiation by agreeing that unless Congress enacted new legislation, automatic (and aggressive) spending cuts would go into effect in 2013. At the time, few people favored the automatic cuts; they saw them as a mechanism to force Congress to do its job. But the sequester did go into effect, and for better or worse it has had major effects on federal spending. The power of the 2011 decision was that it established a drastic outcome if Congress failed to act.
If the goal is to make changes in Social Security, to alter fiscal policy, or even to produce immigration reform, it's possible to imagine a strategy of this kind: With or without the help of a commission, Congress could allow specified reforms to occur on a specified date unless a future Congress says no.
Of course, even when government is divided, a determined president may be able to work out compromises. Maybe we will see such deals during the remaining years of the Obama presidency. Since 2011, however, the nation has faced a harmful combination of daunting challenges and a generally paralyzed Congress. It is imperative to find ways to meet those challenges in the face of persistent divisions.
Cass R. Sunstein, the former administrator of the White House Office of Information and Regulatory Affairs, is a professor at Harvard Law School and a Bloomberg View columnist.