The political calculus may be about to change in Washington with the imposition of the sequester tomorrow. Since the election, President Obama has been on the offensive, Republicans have been in disarray, and polls and pundits have  generally conceded the advantage to the White House. But what happens now?

The president has warned of dire consequences starting right away: long lines at airport  security, flight delays due to furloughed traffic controllers, the inability to deploy defense forces, fewer meat inspections, a 20 percent pay cut for millions of federal workers.  If the president’s warnings come true, then he and Congress will face angry Americans who will have even less interest than they do now in who is to blame.  The approval ratings for both the president and the Congress will fall, but in this scenario the president has much farther to fall and much more to lose.

Instead of pursuing his agenda on immigration and further investments in infrastructure, education and research, the president will face disgust and anger from the American people and media eager to hold him to account. If the warnings turn out to be a negotiating ploy and the pain is delayed or minimized, then the president has spent some credibility and loses his leverage for what one presumes he still wants: a budget deal skewed to his terms.

Either way, Mr. Obama is about to rediscover that the buck stops with him.