GEOFF BENNETT: In the summer of 1980, a prominent Republican close to Ronald Reagan's campaign sought to sabotage then-President Jimmy Carter's reelection by asking Middle Eastern leaders to get a message to the Iranians: Keep the American hostages until after the election, and the Reagan administration will give you a better deal. That stunning reporting this weekend by The New York Times is prompting a rethinking of presidential history. Jonathan Alter details Jimmy Carter's presidency and reelection bid in his book "His Very Best: Jimmy Carter, a Life." Jonathan Alter, thank you for being with us. JONATHAN ALTER, Author, "His Very Best: Jimmy Carter, a Life": Hi, Geoff. GEOFF BENNETT: This reporting by Peter Baker of The New York Times that there was in fact a secret effort by the Reagan campaign to sabotage the Carter campaign by urging the Iranians to hold the American hostages until after that year's presidential election, how does it fundamentally change our understanding of American history and of the Carter presidency? JONATHAN ALTER: Well, this is a pretty big deal, because what you have is the campaign of a candidate for president who is prolonging the captivity of Americans at the U.S. Embassy in Tehran in order to achieve a political victory. Now, this -- the deal itself has not been completely nailed down, but there is considerable circumstantial evidence that this took place. And this latest story is just another piece of that evidence. But it's been accumulating over the years. This was rumored at the time. There was a congressional investigation in 1992 that said there was quite a bit of suggestive evidence, but no smoking gun. And in the time since then, there have been really two major disclosures that have lent credence to this. But it's -- it was an extremely unpatriotic move on the part of William Casey, who was Ronald Reagan's campaign manager and later his director of the CIA. Now, as far as whether the hostages have been released before the election, whether Jimmy Carter would have won, that is unknowable. Jimmy Carter believes so. And the polls were actually much closer than the final result in the weeks just before the election. It turned out to be a landslide. But there were a number of other factors in 1980, including a wretched economy. So we can't know for sure that, if this hadn't happened, history would be different. But we do know for sure that there was a plot by the Reagan campaign to do Carter dirty. GEOFF BENNETT: Well, let me ask you more about that, because The New York Times, Peter Baker in his reporting stresses that there's no evidence that Ronald Reagan knew about this effort or that William Casey directed it. But you wrote a piece this weekend where you said, not only is the reporting credible, but that you, in your own reporting, have encountered information that is even more incriminating. Tell us about that. JONATHAN ALTER: Right. So this is all in my book, my biography of Jimmy Carter. But what happened, Geoff, is that the question of whether there was a so-called October surprise turned on a very, very specific thing in 1992, when it was being investigated by Congressman Lee Hamilton on Capitol Hill. And the question was whether William Casey -- this was Reagan's campaign manager and later CIA director -- whether he left a meeting in London and went to Madrid to meet with four Iranian representatives of the ayatollah to discuss a deal. Now, those four Iranians say that Casey did leave London and did go to Madrid in the summer of 9080, not long before the election. But for a long time, there was no proof of that. And then, just eight, nine years ago now, a document surfaced in President Bush Sr.'s library, where the United States ambassador in Spain said, in a cable, William Casey here this week. We're not sure why. And that pretty much established that he was there for the meeting. And then I have something else in my book that's also very relevant, and that is that a banker and diplomat whose name is Joseph Verner Reed, he later became ambassador to Morocco and head of protocol for Reagan. I came across a letter that he wrote to his family in which he said: I'm proud of my role in preventing the hostages from being released before the election, so that Jimmy Carter would not get credit for that. That's a pretty sick thing, when you think about it. These 52 Americans are being held in captivity. And you have people very close to Reagan -- whether Reagan himself knew or not, we don't know -- but people very close to Reagan who were definitely trying to do this. Whether they completed a deal or not is unclear. The original deal would be that, if the Iranians waited to release the hostages until after the election, which they did, that Reagan would unfreeze their assets and give them arms. It turned out that it was Carter who negotiated the release of the hostages, although -- and this was extraordinary when I came across this. Remember Iran-Contra, where we shipped arms to the Iranians. That was in 1986. This is in 1981, just a couple months after our citizens are released. At that point, the Reagan administration is already shipping arms to its enemy in Iran through the Israelis. So it's quite possible that this was a payoff for the decision by the Iranian government to not release the hostages before the election, which would, of course, aided -- it would have aided Jimmy Carter's reelection efforts. GEOFF BENNETT: Gary Sick, who was, as you know, the Iran expert on President Carter's national security team, he spoke with my colleague John Yang on "PBS News Weekend" yesterday, and said that this reporting basically backs up what they believed to have been the case. You know President Carter, former President Carter. You have interviewed him. What did he think? And how might he view this reporting? JONATHAN ALTER: So, I think that this reporting will be yet more evidence of what both President Carter and Rosalynn Carter expressed to me, which is that they have very strong suspicions that William Casey cut a deal with the Iranians, whether directly or through intermediaries. But they have suspected this for many years, and they have had good reason to do so. GEOFF BENNETT: Jonathan Alter, thanks so much for your time and for your insights. We appreciate it. JONATHAN ALTER: Thanks, Geoff.