Julian Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter" and of the new book "Governing America."

(CNN) -- This week, Republican vice presidential candidate Paul Ryan leveled the ultimate insult at President Barack Obama. He said: "The Jimmy Carter years look like the good old days compared to where we are right now."

In the modern political era, comparing any Democratic (or Republican) president to Jimmy Carter is just about as nasty as a politician can get. The characterization of Carter might not be fair -- as many historians have started to look again at the accomplishments of his term, such as his initiatives on energy and his role in the peace treaty between Israel and Egypt -- but the poor state of the economy on his watch and trouble in Iran and Afghanistan left the Georgian as a symbol of incompetence and failed presidential leadership.

A different way to think about Ryan's statement is to ask a question, one that is equally relevant to Ryan and his future: What is the condition of the Republican Party compared with where it stood in 1980?

On this front, the comparison might not be so kind to the GOP. After all, when Carter's presidency ended, the Republicans had a number of up-and-coming political stars who would soon remake the political landscape, ranging from Newt Gingrich to Ronald Reagan, both in their prime....