Most of the Democrats running for president now would revert once again to multilateralism and internationalism if they took control of American foreign policy. As with the Iran Deal and Paris Agreement, one can consider this worthwhile on substance while also recognizing that the schizophrenic shifting from one approach to the other and then back again does enormous damage to our ability to inspire respect or deference on the part of the rest of the world. Instead, we end up looking confused and incontinent.

The vacillation has even begun to extend to domestic policy, risking a whole different set of negative consequences.

Reagan cut income taxes sharply. Clinton raised them modestly. Bush cut them back and extended them in other areas. Obama raised them slightly again. Throughout this period, the changes from one administration to another were relatively minor. But then Trump and the Republican Congress passed an enormous corporate tax cut, dropping the rate of tax paid by businesses from 35 percent to 21 percent, its lowest rate since 1939.