DENVER (AP) - Democrats are poised to formally declare Barack Obama the first black presidential nominee of a major party.

While the historic outcome is certain, suspense remains over how the vote by delegates will proceed, and for how long.

House Speaker Nancy Pelosi is the presiding officer of the Democratic National Convention. She predicts that the roll-call voting after the names of both Obama and one-time rival Hillary Rodham Clinton are put in nomination will go "very smoothly."

However, many details remain unknown, including how many states will vote before somebody -- probably Clinton herself -- asks the delegates to give the nomination to Obama by acclamation.

Clinton plans to meet with all her delegates this afternoon and is expected to make a statement at that time.

Obama is due to arrive in Denver today. He will give his acceptance speech tomorrow to as many as 75,000 people at nearby Invesco Field at Mile High Stadium.

(Copyright 2008 by The Associated Press. All Rights Reserved.)