Mr. Clinton lowered the capital-gains tax rate; Mr. Obama has proposed raising it. Mr. Clinton cut spending and produced a surplus. Under Mr. Obama, spending and the deficit reached record levels. In foreign policy, Mr. Obama has shown himself to be far more critical of traditional allies and more supine toward our adversaries than Mr. Clinton was. Mr. Obama has often acted as if American strength is a problem to which the solution is retrenchment, or even retreat.

Another bellwether: Hillary Rodham Clinton, in positioning herself for the 2016 election, is decidedly more liberal than she and her husband once were on illegal immigration, gay marriage and incarceration. She has called to “end the era of mass incarceration” and spoken about the importance of “toppling” the wealthiest 1 percent. She has remained noncommittal on the Trans-Pacific Partnership, the free-trade agreement that has drawn ire from the left.

The Democratic Party, then, has moved steadily to the left since the Clinton presidency. In fact, since his re-election, Mr. Obama’s inner progressive has been liberated. (An exception is the administration’s conditional approval of oil drilling off the Alaskan coast, starting this summer.) Other examples are his executive action granting temporary legal status to millions of illegal immigrants, his claim that gay marriage is a constitutional right, and his veto of legislation authorizing construction of the Keystone XL pipeline.