Republicans like their odds on taking control of the Senate in these midterm elections. “The tea leaves are clear: It is going to be a very good Republican cycle,” declares GOP pollster Bill McInturff, who helps conduct the Wall Street Journal/NBC News poll.

The Senate is the big prize in this fall’s voting, of course, and losing the chamber to Republicans, giving them full control of Congress, would represent a terrible outcome for the Democratic Party.

Oddly, though, it might not be such a bad outcome for one particular Democrat: President Barack Obama.

How can that be? A look back shows that eras of evenly divided power—Congress fully controlled by one party, the presidency by the other—have turned out to be among the most productive. And if you are a president yearning for elusive legislative achievements in the final two years of your term, anything that makes Washington more productive would be welcome, even if attaining some of that productivity required trimming your ideological sails.