It depends.  But I will argue that the thing it depends on is probably different from the thing that most people believe is important.

When I was young, I looked at this issue in partisan terms.  Divided government is good (I thought) if the party I oppose holds the presidency, and united government is good if my preferred party holds the presidency.  I suspect that this is a fairly widely held view, especially among better educated voters.  But I now think this is wrong.

I have come around to the view that the decisive factor is not “which party holds the presidency”, rather the optimal outcome depends on the answer to this question:

Is this an era of relatively good governance, or an era of relatively bad governance?

If we are operating in an era where governments are engaged in useful reforms, such a deregulation, privatization, freer trade, fiscal responsibility and tax reform, then a more powerful central government may (and I emphasize may) be a good thing.  If we are operating in an era of socialism and nationalism, then more government power is usually a bad thing.

Because most of this blog’s readers live in the US, I won’t use an American example to make this point.  It’s too hard to look beyond our own personal political biases.  Instead, I’d ask you to look across the pond and contemplate recent British history.

They’ve had three relatively long periods of mostly one party rule.  The Conservatives ruled from 1979-1997, then Labour from 1997-2010, and then the Conservatives ruled again until this past summer’s election.  What do we notice about these eras?

1. Governments often do better in their early stages.  They come into office with a plan to fix the failures of the previous administration, and often do some useful things during the early portion of their tenure.  Then they run out of gas, and policymaking quality deteriorates.

2. Governments tend to do better policymaking when the global zeitgeist is moving in a “neoliberal” direction (say up until 2007), and less effective policymaking when the world is moving in an illiberal direction.

I certainly won’t tell people how to vote, and indeed in a presidential year one cannot know for certain whether one’s vote would lead to unified or divided government.  (In midterm elections, voters do know.)  But one thing to consider might be whether we are in an era of good governance or bad governance.  Is the political zeitgeist moving in the direction of balanced budgets and supply side reforms, or is it moving in the opposite direction? How much trust do you have in the policymaking process of today’s America?

One final point.  I would not rule out the possibility that divided government is good more often than it is bad.  That largely depends on the question of how much “activism” you favor.  My own view is somewhat hostile to government activism, thus my bias is toward divided government.  In this post, I’m merely trying to describe when each outcome is relatively more important, not necessarily which is best in an absolute sense.  If I favored government activism, I might lean toward the view that unified government is usually best.  Even so, I think people tend to underestimate the importance of the zeitgeist, the importance of whether we are in an era of relatively good governance, or an era of relatively bad governance.