DENVER — Democrats on Wednesday paid homage to their past by listening to an invigorating valedictory by former President Bill Clinton and then gazed to their future as portrayed by newly minted vice presidential nominee Joe Biden.

And Barack Obama made a (somewhat) surprise early visit to the Democratic National Convention after becoming the first man of color to receive a major party's nomination — which came as Hillary Clinton moved to nominate him by acclamation. Obama briefly praised convention performances so far and promised more.

Obama was officially named the candidate earlier in the day, in a historic moment that had many people, especially older delegates who had grown up in a segregated society, visibly weeping.

"We've done pretty well so far," Obama said to thunderous applause. "Michelle Obama started it off pretty well. ... Hillary Clinton rocked the House last night. ... Bill Clinton reminded us what it is like when you actually put people first."

He invited everyone to the INVESCO Field at Mile High for his speech tonight, saying, "We're going to have a great time tomorrow night, and we're going to see you there."

Obama's early sneak-peek appearance was reminiscent of similar visits made by Bill Clinton and John F. Kennedy to conventions when they were first nominated, and Democrats hope Obama will have the same later electoral success as they did.

On Wednesday, it was Biden's turn to depict a bright future he sees if Obama is elected, and a bleaker version if Republican John McCain wins.

"The choice in this election is clear. These times require more than a good soldier (referring to former Navy pilot McCain) — they require a wise leader: a leader who can deliver change, the change everybody knows we need. Barack Obama will deliver that change," the senator from Delaware said.

Biden added about Obama, "I watched how he touched people, how he inspired them, and I realized he has tapped into the oldest American belief of all: We don't have to accept a situation we cannot bear. We have the power to change it."

Biden said when he was young and his working class family struggled in tough economic times, his father would tell him, "Champ, when you get knocked down, get up." Biden added, "Millions of Americans have been knocked down. And this is the time as Americans, together, we get back up."

Biden, chairman of the Senate Foreign Relations Committee, took many shots at McCain for positions on foreign policy that are opposite to Obama's, including his long opposition to setting a firm time for withdrawing troops from Iraq.