The conventions are over, but the individual who will determine the 2012 election didn’t attend either of them. His name is George W. Bush.

Conventional wisdom holds that elections are about the future. Or about the personalities of the candidates. Or at least about voters’ perceptions of the last four years. But a quick glance at history shows that’s not always so. Republicans won every election between 1868 and 1880—not because Ulysses S. Grant, Rutherford B. Hayes, and James Garfield were such fabulous candidates, and not because their Democratic opponents were so awful. Nor did they win because of the conditions in the country at the time. They won because when Americans thought about the Republican Party, they thought about Abraham Lincoln. And when they thought about the Democrats, they thought about Jefferson Davis.

The same thing happened after the New Deal. In 1948, Harry Truman was personally unpopular and Americans were in a foul mood. But Truman won in large measure because of the way Americans felt about the Democratic and Republican parties, impressions created less by him or his GOP opponent, Thomas Dewey, than by two guys named Roosevelt and Hoover, who had faced off in 1932. The same was true in 1988, when George H.W. Bush, a weak candidate in his own right, made his race versus Michael Dukakis another referendum on Ronald Reagan versus Jimmy Carter.

The point, as Walter Dean Burnham and other political scientists have noted, is that not all presidential elections are created equal. Some create a realignment—a shift in public perception of the two parties—that then frames the elections after that. In this era, Bill Clinton began that realignment by ameliorating the Democrats’ reputation as fiscally irresponsible and soft on national security, welfare, and crime. By Clinton’s second term, when asked which party they felt more favorable toward, Americans gave Democrats a double-digit advantage. Then George W. Bush was elected, presided over catastrophes in Iraq, the financial system, and the Gulf Coast—and the GOP’s public image nosedived. Democrats haven’t maintained all the good will they racked up in the Clinton era, which isn’t surprising given the lousy state of the economy. But neither have Republicans rebounded much from their Bush-era collapse. And the result is a Democratic advantage, especially among rising demographic groups like Hispanics and the young.

Mitt Romney is not a great candidate; Barack Obama is a better one. But without the Bush legacy, Romney would be leading this race. His problem is that except among staunch conservatives, Bush has so hurt the GOP’s brand that Romney doesn’t look like the fresh economic fix-it man that Republicans want to portray him as. Instead, it’s all too easy for Democrats to paint him as George W. Bush the 3rd, just as they painted John McCain as George W. Bush the 2nd.

Romney has tried to handle the Bush legacy the same way McCain did: by ignoring it. When Republicans convened in late August in Tampa, as in Minneapolis in 2008, Bush was not there. But in campaigns, ignoring your weaknesses rarely makes them go away. While at their convention Republicans tried to pretend that the Bush presidency never happened, the Obama campaign handed Bill Clinton the microphone and allowed him to define the race as Obama-Clinton versus Romney-Bush. The GOP, in Clinton’s narrative, creates economic messes. Democrats clean them up.

Historically, the candidates who win when their parties are unpopular are those able to create strong, distinct personal brands. Eisenhower wasn’t just some generic Republican. He was the general who liberated Europe. And he couldn’t be painted as Hoover redux because he basically embraced the New Deal. In 1992 Clinton ran as a New Democrat (i.e., not Jimmy Carter) who rejected his own party’s dogmas on crime, welfare, and foreign policy.

Romney’s problem is that like Dewey in 1948 or Dukakis in 1988, his personal brand is weak. To win the primaries and gin up core conservative support, he has amputated those parts of his political persona that might have allowed him to come across as something other than a generic Republican. And unfortunately for him, when Americans think of a generic Republican today, they still think of George W. Bush.

One day, a Republican presidential candidate will exorcise Bush’s ghost. But most likely, he or she will do so by bluntly telling Americans where Bush’s presidency went wrong, and how their presidency will be different. Until that happens, George W. Bush will be present at every Republican and Democratic convention for years to come, whether anyone invites him or not.