As his campaign threw out unsubstantiated charges that Mitt Romney might be guilty of a felony and then mocked Romney’s off-key singing of “America the Beautiful,” President Obama took a moment to reflect on the sad state of America’s political tone. “Washington feels as broken as it did four years ago,” he explained. “And if you ask me what is the one thing that has frustrated me most over the last four years, it’s not the hard work. It’s not the enormity of the decisions. It’s not the pace. It is that I haven’t been able to change the atmosphere here in Washington to reflect the decency and common sense of ordinary people.”

The problem is real enough. Extreme political polarization is the product of democracy that undermines democracy. It increases incivility and magnifies distrust of government. It causes some to abandon civic engagement in disgust, and others to join angry ideological insurrections. In Congress, it adds to the obstructive power of cohesive partisan blocs and makes bargaining and compromise in the public interest more difficult.

Do politicians cause this polarization or merely reflect it? There are plenty of contributing factors they don’t control. The public itself has become more partisan over the last few decades. Both parties have become more ideologically homogeneous (though Democrats still have more internal diversity). The growth of partisan media has fed polarization.

But leaders can oppose this trend or contribute to it. Things get worse when Rep. Allen West, R-Fla., claims there are “about 78 to 81 members of the Democratic Party that are members of the Communist Party.” Or when Rep. Debbie Wasserman Schultz says that Republicans “want to literally drag us all the way back to Jim Crow laws.” Politicians can legitimize incivility, contempt and conspiracy theories. One academic calls such leaders “polarization entrepreneurs.” They increase their status and influence by feeding partisan division.

Whatever his intentions or provocations, Obama is now engaged in partisan polarization on an industrial scale. His campaign’s latest round of Bain charges is not politics as usual. It is the accusation of criminal impropriety — the filing of false government documents — without real evidence, as various fact-checking outfits have attested. Obama’s recent attack ad, “Firms,” reflects the sensibilities of a particularly nasty 13-year-old. It is difficult to imagine most Americans saying: “That is just what American politics most needs — more juvenile viciousness.”

These are not excesses; they are the essence of Obama’s political strategy. He is attempting to destroy Romney before Romney can define himself, while using a series of issues — the mini-DREAM Act, voting rights and contraceptive controversies — to excite his base. The approach is not politically irrational. But it is premised on the avoidance of issues such as unemployment and the deficit. And it leaves little room for complaints about the brokenness of Washington.

Will this strategy succeed? So far, it hasn’t seemed to change the fundamental dynamics of the race, which remains both very close and remarkably stable. Negative charges usually work when they have the ring of truth, and Romney — though he has his weaknesses as a candidate — does not fit the part of a sleazy businessman or a Nixonian liar.

But these tactics do have an effect on politics. The most partisan Democrats are encouraged and empowered. The most partisan Republicans gain an excuse for the next step of escalation. This is the nature of polarization: Both sides feel victimized, which becomes a justification to cross past limits and boundaries. Neither side feels responsible for the problem, while both contribute to it.

Obama and his political team have a history of viewing themselves as superior to Washington and the “Beltway mentality.” The president combines a feeling of superiority to politics with a determination to beat his opponents at their own grubby game. It allows him to view himself as a pure, transformative figure while employing the tactics of a Chicago pol.

It is also one reason, according to Gallup, the gap between partisans’ approval ratings of Obama has been “historically high.” This does not mean the GOP bears no responsibility. It only means Obama has made Washington more broken and continues to make it more broken — both responding to grievances and creating new reasons for grievance.

Meanwhile, America is well on its way to a disturbing destination: A nation with the responsibilities of a superpower and the politics of a banana republic.

Michael Gerson’ is a columnist for The Washington Post. His email address is George Will is on vacation.