Up until Thursday night it had been a crowded week for the Democratic National Convention. There were too many delegates and 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 70,000 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 sense of history and horizon that had seemed lacking in recent weeks.