National unity. As a candidate for president, Obama promised to soothe America’s bitter and divisive politics, and to replace red state/blue state animosity with cooperation and bipartisanship. But the healer-in-chief millions of Americans voted for never showed up.

According to Gallup, Obama became most polarizing president in modern history. Like all presidents, he faced partisan opposition, but Obama worsened things by regularly taking the low road and disparaging his critics’ motives. In his own words, his political strategy was one of ruthless escalation: “If they bring a knife to the fight, we bring a gun.” During his 2012 reelection campaign, Politico reported that “Obama and his top campaign aides have engaged far more frequently in character attacks and personal insults than the Romney campaign.” And when a Republican-led Congress wouldn’t enact legislation he sought, Obama turned to his “pen and phone” strategy of governing by diktat that polarized politics even more.

To his credit, Obama acknowledges that he didn’t live up to his promise to reduce the angry rancor of Washington politics. Had he made an effort to do so, perhaps the campaign to succeed him would not have been so mean. And perhaps 60 percent of voters would not feel that their country, after two terms of Obama’s administration, is “on the wrong track.”

Obama’s accession in 2008 as the nation’s first elected black president was an achievement that even Republicans and conservatives could cheer. It marked a moment of hope and transformation; it genuinely did change America for the better.

It was also the high point of Obama’s presidency.