In making these assertions, I’m not engaged in casual speculation — I’m drawing on a large body of political science research, mainly focused on presidential contests in the United States but clearly applicable elsewhere. This research debunks almost all the horse-race narratives beloved by political pundits — never mind who wins the news cycle, or who appeals to the supposed concerns of independent voters. What mainly matters is income growth immediately before the election. And I mean immediately: We’re talking about something less than a year, maybe less than half a year.
This is, if you think about it, a distressing result, because it says that there is little or no political reward for good policy. A nation’s leaders may do an excellent job of economic stewardship for four or five years yet get booted out because of weakness in the last two quarters before the election. In fact, the evidence suggests that the politically smart thing might well be to impose a pointless depression on your country for much of your time in office, solely to leave room for a roaring recovery just before voters go to the polls.
Paul Krugman, Economics and Elections – NYTimes.com.