After an Obama bounce prompted a wave of articles about Romney’s dwindling chances, Romney’s pollster Neil Newhouse published a memo detailing the case for a comeback. Perhaps the most striking element of the memo was the complete absence of polling data, but his strained reconceptualization of the 1980 race was also highly unusual. Newhouse contended that Carter led by nearly 10 percentage points in late October and asserted that this year would see a rerun of that campaign. While the myth of a Reagan comeback figures prominently in American electoral history, it turns out that it’s just that: a myth.

The legend of Reagan’s epic comeback is largely the result of anomalous Gallup polling, which even showed a Carter advantage over the final month of the campaign. But if RealClearPolitics or had existed in 1980, the conventional wisdom would have been a little different. In fact, Reagan held a lead from mid-September onward and had a two or three point lead heading into the debates. Private polling conducted for the Reagan and Carter campaigns showed the same thing. Reagan’s 10 point victory is a precedent for sweeping undecided voters, but it isn’t a model for a come-from-behind victory (I am hardly the first to make this observation, as John Sides and Greg Sargent have been leading this charge for some time).

The problem for Neil Newhouse, of course, is that without the 1980 model, there isn’t any example of a challenger coming from behind to defeat an incumbent president. The leader of mid-September polls has gone onto win the popular vote in every election since 1948, and then it was the incumbent who pulled off the comeback. Now, unprecedented obviously doesn’t mean impossible. Only ten post-war presidents have run for reelection and there aren’t many lessons to be gleaned from the predestined blowouts where an incumbent continuously holds a substantial lead through November, leaving us with only five interesting races involving incumbents: 1948, 1976, 1980, 1992, and 2004. And if you ask me, 1976 and 1948 aren’t entirely analogous, since Ford and Truman were running for the presidency for the first time.

But many still interpret 1980 as a favorable precedent for Romney, since it is proof that a race can change in the final days. But in retrospect, the signs of Reagan’s big victory were apparent well in advance of his actual surge, and that isn’t true for Romney today. Reagan’s post-convention bounce foreshadowed his eventual finish, as he seized nearly 50 percent of the vote compared with his final tally of 51 percent, and above the 46 percent threshold for victory in a year when John Anderson would take more than 8 percent of the vote. In every post-war election involving an incumbent, the winning challenger has seized a majority of voters after his convention. Unlike George W. Bush and Reagan in 1984, Carter did not cancel out his opponent’s bounce with a larger one of his own. While Reagan’s lead vanished after the DNC as many of Reagan’s supporters returned to the undecided column, Carter only edged up to the upper-thirties or low-forties, presaging his eventual 41 percent finish.

Reagan quickly reclaimed the lead after the DNC (if he ever lost it), but it wasn’t until the end of the campaign that most voters who indicated their support for Reagan following the RNC returned to his side. In retrospect, this should have been predictable. The voters that flocked toward Reagan already demonstrated their willingness to vote for him, never indicated any intention of voting for Carter following the DNC, and uniformly disapproved of the president’s performance. Check out this chart from John Sides:

A similar pattern occurred in 2004. Kerry won the debates and latent Kerry voters that supported him after the DNC but became undecided after the RNC returned to his side. Conversely, many of Bush’s post-RNC supporters returned to undecided. But on Election Day, Bush won 50.7 to 48.3—a result that mirrored Bush and Kerry’s respective bounces, just as the 1980 results mirrored Reagan and Carter’s bounces.

In races involving a well-known incumbent unlikely to be redefined over the final months of the campaign, the conventions represent a fleeting moment when persuadable voters flock to their eventual corners, hinting at the ultimate outcome. My general presumption toward the so-called fundamentals reinforces this interpretation. The fundamentals don’t predict the results with precision, but they powerfully shape the contours of the race, making it difficult to sway voter preferences about an incumbent once they’re established.

As a result, Romney is in a much worse situation than Reagan. Unlike Carter, Obama has inched close to 49 percent of the vote in the RealClearPolitics average, which puts him in striking distance of reelection. Even if Romney could pull-off a Reagan-esque surge among undecided voters, it would just result in a dead heat. And unlike Reagan, Romney didn’t demonstrate that a majority of voters were prepared to dismiss the president by reaching or surpassing his own magic number after the RNC. Instead, 2012 looks more like 2004.

If Romney can’t take a lead over the next week or so, he will be forced to do something never successfully attempted: mount an unprecedented comeback against an incumbent president. As mentioned before, the absence of precedent doesn’t mean something is impossible, especially since the race is close. But it might speak to probability, and I hope a hypothetical Romney comeback will be properly appreciated as a first in the history of presidential politics. Maybe then we’d finally be able to move on from the myth of 1980.