Last night Barack Obama defied history and the physics of politics and wrote a new chapter. Despite being weak on the most important issue to the voters, the economy, he won rather easily? Why?

In no particular order:

1.The economy wasn't the  killer issue many expected. The electorate took a more complex view of the economy than expected. Instead of simply blaming the incumbent, exit polls said they agreed with the Obama premise that George W. Bush had left the country a mess. Moreover, exit polls showed that more Americans believe the economy is getting better than worse.

 2. The Republican brand was hijacked this cycle by the tea party and social extremists. Obama's victory coalition of women and minorities (on track to become the majority) is what the future of American politics looks like. To put it mildly, Republicans in general and Mitt Romney specifically took hostile positions on immigration and women's health. Romney sent so many negative signals: from his causal comment in a primary debate about his lawn maintenance company hiring undocumented workers (he sounded like a hacienda owner) to defunding Planned Parenthood to the infamous “47 percent” statement.

 In this cycle, too often, the Republican answer to this demographic change was either to deny it or to suppress its vote.

3. The Obama campaign's theory of the race was right in almost all details. The campaign did, indeed, build the most sophisticated voter ID and turnout machine ever, and it used the auto bailout to build a firewall in Ohio, which it didn't even need in the end. Many Republicans embarrassed themselves in the final weeks of the campaign spinning turnout scenarios, putting new states in play and predicting a Romney landslide. There will be some angry investors to contend with in the Republican super PAC ranks; they were told they were buying a winner. Let those recriminations begin.

 4. Romney badly damaged himself in the primaries, and he didn't pivot to the middle until it was too late. Perhaps he was paralyzed by the fear that he would be labeled the Etch-a-Sketch candidate; perhaps he believed he needed to consolidate a fractured Republican base and appease the party's distrustful right wing.

Last night, Mr. Obama was given something rare and precious in politics: a second chance. And he was granted it with more enthusiasm than many anticipated. As I argued yesterday, I think he is well-positioned to make the most of it.  He and his supporters are freed from impossible expectations and naive dreams of transformation. But while laying down one burden, he picks up another. What will his legacy be?