President Obama’s reelection has triggered a flood of analysis about his ability to put together a winning coalition. Some have argued that America has fundamentally shifted in such a way that it will become increasingly difficult for Republicans to win national elections. The fact that Obama was able to win not just once, when Americans were rebelling against the Bush era, but a second time, even with a weak economy and a difficult record to defend, merits serious consideration. But a deeper analysis must also probe into whether the winning coalition Obama put together in the last two elections says more about his personal appeal and status as an historical figure than it does about the changing nature of the American electorate. Specifically, a key question is whether future Democratic candidates will be able to command the type of margins Obama enjoyed among young voters and blacks.

To delve into this question, I went back into the Roper Center’s archives of exit polling data, and compared it to data from Obama’s victories in 2008 and 2012. Not surprisingly, Democrats have consistently dominated Republicans among black voters and have generally had the edge with younger voters. But Obama has significantly outperformed his Democratic predecessors among both groups.

In the six presidential races between 1984 and 2004, Democrats average victory margin among black voters was 77 points, and it never reached higher than Walter Mondale’s 82-point victory over Ronald Reagan. But in 2008, Obama won black voters by 91 points, and in 2012 he won them by 87 points. Since 1992, when comparable data was available, Democratic presidential candidates won 18 to 24 year olds by an average of 11.5 points and 25 to 29 year olds by 7.25 points. Yet in 2008, Obama won the two groups by 34 points and 35 points, respectively, and in 2012, though down, those groups still gave Obama the edge — by 24 points and 22 points.

So what kind of effect did this have? Given that 18 to 29 year olds made up 19 percent of this year’s electorate and blacks made up 13 percent, a big one. A rough calculation finds that if Obama’s performance among these groups were consistent with John Kerry’s level in 2004 — or that of the typical Democrat in recent elections — he would have lost Ohio and Florida. Add in young voters, and Romney likely would have won Virginia, too, and possibly even Colorado, which would have given Romney 275 electoral votes, enough to win the presidency. (It’s tough to make a precise calculation, because the two groups cannot simply be added, because some voters are both black and in the 18 to 29 year old age range.)

What we won’t know until 2016 and beyond is whether Obama’s outsized performance with these groups can be repeated with a different Democratic candidate at the top of the ticket. The election of the first African American president was understandably a moment of great pride for the black community. Will Obama’s legacy help ensure that black voters give future Democratic presidential candidates the same margins they gave him? Or will their vote patterns revert to pre-Obama levels? As far as young voters are concerned, is it the Democratic Party’s platform simply more appealing? Or is it Obama that’s appealing to them? Though Democrats usually do better among younger voters, the group’s voting patters have tended to be more erratic and personality driven. Reagan trounced Mondale with young voters in 1984, for instance, while Bill Clinton blew out Bob Dole in 1996. Four years after Clinton’s dominant performance with young voters, his vice president, Al Gore, barely edged out George Bush with the same demographic.

To be clear, I’m not suggesting Republicans simply chalk up the past two presidential elections to a cult of personality, using it as an excuse to ignore the warning signs from this election. As I argued earlier today, Mitt Romney’s dismal performance among the growing Hispanic population made the race essentially unwinnable. Also, it’s important to keep in mind that though Bush won twice, he enjoyed extremely fragile Electoral College victories both times. Republicans haven’t had a convincing win at the presidential level since 1988, and the number of states that they’ve been able to put into play has continued to shrink.

So, Republicans have some serious soul searching to do. But at the same time, it remains to be seen how sustainable the Democrats’ winning coalition is beyond Obama.