Britain’s economic performance since the financial crisis struck has been startlingly bad. A tentative recovery began in 2009, but it stalled in 2010. Although growth resumed in 2013, real income per capita is only now reaching its level on the eve of the crisis — which means that Britain has had a much worse track record since 2007 than it had during the Great Depression.

Yet as Britain prepares to go to the polls, the leaders of the coalition government that has ruled the country since 2010 are posing as the guardians of prosperity, the people who really know how to run the economy. And they are, by and large, getting away with it.

There are some important lessons here, not just for Britain but for all democracies struggling to manage their economies in difficult times. I’ll get to those lessons in a minute. But first, let’s ask how a British government with such a poor economic record can manage to run on its supposed economic achievements.

Well, you could blame the weakness of the opposition, which has done an absolutely terrible job of making its case. You could blame the fecklessness of the news media, which has gotten much wrong. But the truth is that what’s happening in British politics is what almost always happens, there and everywhere else: Voters have fairly short memories, and they judge economic policy not by long-term results but by recent growth. Over five years, the coalition’s record looks terrible. But over the past couple of quarters it looks pretty good, and that’s what matters politically.