FDR's New Deal programs are well known, but if you ask most students what they don't know is that the Supreme Court overruled and discontinued many of them. This is a good NPR piece on how FDR tried to find ways to get around them!
Roosevelt, however, didn't endorse the ideas that Congress or the American public should be able to override the Supreme Court.
"He didn't think it was practical," says Shesol. "It takes a very long time, usually, to amend the Constitution ... enough to change the reality in the country. But secondly, and this is really important in understanding why Roosevelt packed the court, [is that] he didn't see any kind of contradiction between the Constitution and the New Deal. He didn't think there was anything in the Constitution that prevented him from doing what he needed to do. The problem as he saw it was not the Constitution; it was the conservatives on that particular Supreme Court. So what could you possibly do about them? So that's how he came to the idea of packing it."
Roosevelt's idea was that for any justice over the age of 70 who refused to retire, the president could appoint a new justice to sit beside the current justice and do his work.
"If the plan passed and no one [on the current court] retired, Roosevelt would instantly get to appoint six new liberal justices to the Supreme Court," explains Shesol. "Because he couldn't push the conservatives off the court, he thought, 'Well, at least I can outnumber them.' And what most people didn't realize then or today is that this is entirely constitutional. There's nothing in the Constitution that sets the number of justices at nine. The Constitution says nothing about how many justices.