So why do American politics seesaw back and forth? Some of what I’ve captured might be attributed to the well-known phenomenon of midterm loss: The party of the president tends to lose seats in a nonpresidential election. But it is unclear if midterm electoral backlashes are a certainty or a response to a president’s specific policy agenda. This can be hard to disentangle as new presidents often pursue big agendas in the hopes of shaping policy in their ideological mold.

For instance, after campaigning on health care helped President Obama win votes in 2008, voters in the 2010 election punished legislators who supported the Affordable Care Act because they came to view the policy and the legislators as too liberal. But backlashes may materialize even when large agenda items fail to pass, such as the response to Clinton’s health care proposal in the 1994 election or to Bush’s Social Security proposal in the 2006 election.4

But there is a deeper problem: Neither party seems capable of sustaining a public majority to carry out its governing vision to completion.