This question came to mind through an Op-Ed catechism in the New York Times recently. First, as part of a broader analysis of the contemporary Republican Party's ability to win elections but not produce results for the American people, Ross Douthat decreed that Mr. Carter, the last president elected by the old New Deal coalition of Democratic voters, "got nothing done." Second, in response to this statement, Carter's former domestic policy adviser, Stuart Eizenstat, wrote a letter the Times published that listed Carter's many achievements in office.
The "got nothing done" analysis by Douthat is curious on its face. After all, the conservative critique of Carter back in the day was something to the effect that Carter was destroying America by pushing it too far to the left--in other words, the same sort of rhetorical drivel they have been delivering for the past 70 years, up to and including today. You can agree or disagree with that rhetoric--I'll leave it to your imagination to decide how I feel about it--but you can't say it's the same thing as getting "nothing done."
On the other hand, Eizenstat's entirely accurate and concise description of Carter's accomplishment's in office only begs my titular question even further. Usually, the answer you get are (a) stagflation, and (b) the Iranian hostages. Both of these crises were outgrowths of bad foreign policy decisions encouraged by conservatives that had the effect of making the United States unusually dependent on oil-producing (i.e., Arab) countries for the maintenance of our way of life. And the hostage crisis was deliberately manipulated, and even prolonged, by Republicans and their conservative supporters for purely partisan purposes.
And Carter devoted much of his presidency to ending that dependence, describing the struggle to do so as the moral equivalent of war. As we subsequently saw on 9/11, it was in fact the literal equivalent.
I think the ongoing Carter-hatred is based largely on a recognition even by conservatives that the critique of Carter that emerged during the 1980 election campaign was and remains a gargantuan lie--and that this lie is coming back to haunt them, now that their own coalition is fracturing just as the New Deal coalition fractured during Carter's term. Despite that fracturing, Carter pulled off a number of significant legislative and diplomatic accomplishments, accomplishments that still benefit the American people even today. Trump, meanwhile, apart from one purloined Supreme Court seat, is bereft of anything that could be called an accomplishment--unless attempting to install a kleptocracy in the White House counts.
And yet Trump, like Carter, clearly appears to be a president of preparation for a major change in the politics of this country. The question is, can the Democrats produce a Reagan to make that change a reality? I wish I had a positive answer to that question. I pray that such an answer will emerge before 2020.