Was James Buchanan the worst U.S. President?

The general scholarly consensus is that he was among the worst, if not the worst, President in American history. The main reason for this assessment is that Buchanan failed to prevent the country's slide towards civil war. Instead of stepping up to the plate and showing leadership when the United States needed it most, he openly sided with the South—whose voters had helped him get elected—thereby antagonizing Northern opinion and driving the country further and further apart.
To be fair to Buchanan, the issue of slavery had been a running sore in American politics for decades. But instead of taking active steps to try and deal with the problem and the huge sectional divisions it had generated, the hidebound, stubborn, and not very imaginative Buchanan made a bad situation a whole lot worse than it might have been. Hence his deserved reputation as one of the very worst occupants of the White House.