Until Thursday night, it had been a crowded week for the Democratic National Convention. There were too many delegates and too many reporters jammed into the too-small Pepsi Center. The conversations of the faithful were crowded with anxieties about slipping poll numbers, soft messaging, elusive unity, and the omnipresent Clintons. Memories of disastrous Augusts (John Kerry in 2004, Al Gore in 2000 and Michael Dukakis in 1988) pinched the party’s imagination.

Tonight those hemmed-in feelings dispersed into the breezes of mammoth Invesco Field, where an adoring throng of 84,000 cheered Barack Obama as he accepted his party nomination with a speech– none too lofty and none too soft–that reinfused his historic campaign with a sense of history and horizon that had seemed lacking in recent weeks.

Early on Obama declared “enough,” and that word resonated throughout his 48-minute speech. So did the phrase “Now is the time.” Those simple sentiments bookended a comprehensive indictment of Republican presumptive nominee as honorable but clueless (“It’s not that John McCain doesn’t care. It’s that he doesn’t get it.”) and challenges to his own party (“Democrats, Democrats, we must also admit that fulfilling America’s promise will require more than just money”).

Tough talk on Afghanistan (“We must take out Osama bin Laden and his lieutenants if we have them in our sights”) was combined with tender feelings toward his grandmother (“She poured everything she had into me”).

After delivering a laundry list of specific policy proposals, Obama returned to the post-partisan rhetoric that helped him prevail over the more traditional style of Hillary Clinton in the Democratic primaries.

“These — these are the policies I will pursue,” he declared in summation. “And in the weeks ahead, I look forward to debating them with John McCain.”

“But what I will not do,” he went on, “is suggest that the senator takes his positions for political purposes, because one of the things that we have to change in our politics is the idea that people cannot disagree without challenging each other’s character and each other’s patriotism.”

“I’ve got news for you, John McCain,” he finished. “We all put our country first.”

Thus did Obama put a partisan edge on his postpartisanship. He sharpened the choice facing voters 68 days from now without closing the door to his appeals to Republicans and independents. He again demonstrated the political agility that brought him to this historic occasion and almost certainly restored his supporters’ confidence that was a little shaky just a few hours earlier.