At a moment when the president of the United States could have, and should have, stepped up to his responsibilities as leader of the greatest nation on earth — on a day when the American people and the world looked to him for reassurance and vision — Barack Obama chose to indulge himself in yet another round of petty, cynical partisanship.

Apparently, the president’s only purpose in demanding 15 minutes of Monday night television time for a speech on the looming debt-ceiling crisis was to blame former President George W. Bush for the national debt and set up congressional Republicans to take the fall for whatever bad things happen if the debt ceiling isn’t raised by next Tuesday.

Obama, who seems less interested in leading the country than in gearing up for his 2012 re-election campaign, accused Republicans of pushing the United States toward a first-time-ever default on its financial obligations — and with every self-serving word pushed the country closer to a first-time-ever default on its financial obligations.

As the deadline for “default” draws closer, of course, the previously untold truth — that actual default is not on the immediate horizon, even if the nation’s borrowing limit is not increased by Aug. 2 — is beginning to emerge.

There were news reports on Tuesday, in fact, that White House officials were privately reassuring bankers there would be no default, even as the president was telling the American people that default was imminent.

Obviously, the term “default” is open to interpretation. Technically, the government would default only if it failed to meet the payments on money it has borrowed, and no one expects that to happen on Aug. 3 or for some time after that.

In order to make the debt payments, however, the country would likely “default” on other obligations, and President Obama has mentioned Social Security recipients as early targets of nonpayment.

So this is a serious game the folks in Washington are playing, no matter what the terminology and no matter how the blame is divvied up.

Even more daunting than the short-term turmoil resulting from missed Social Security payments or military personnel not getting paychecks would be the long-term damage to the economy if markets and investors lose faith in America’s financial stability. That would be the catastrophe so many experts have predicted if the debt-ceiling dispute is not resolved.

It might seem unfair to single out the president for criticism. Republicans, after all, have been stubborn, if not intransigent, in their demands for budget cuts and their resistance to tax increases as part of any agreement to raise the debt ceiling.

But we expect better from the president of the United States. Obama likes to portray himself as the lone adult among reckless, food-fighting adolescents in these disputes, so it seems only reasonable to ask him to act the part.

If he’s the only politician at the negotiating table who truly understands the potential consequences of a failure to compromise, then he should be the one to compromise.

Instead of using his speech Monday night to childishly urge the American people to swamp Republican switchboards with phone calls supporting his position, Obama should have stood before the nation and offered a viable plan for solving the problem.

If he wanted to put pressure on Republicans to make a deal, he should have publicly offered a deal they could accept.

Instead, he hurled insults at the other side and fed the gridlock. It’s a tactic he has employed throughout his presidency. He apparently believes it will help him get re-elected.

And that, sad to say, seems to be the only thing he cares about.