Denver ? On the eve of the Democratic National Convention, Barack Obama said Sunday he hoped a week of political speechmaking would persuade reluctant middle-class voters to swing behind his bid for the White House, while Republicans sought to stir discontent among Hillary Rodham Clinton’s supporters.

Clinton was having none of it. In a gesture of unity, Obama’s rival in the bruising battle for the nomination was expected to release the delegates she won in primaries and caucuses, telling them in midweek they are now free to join her in supporting the victor.

Obama, bidding to become the first black president, campaigned through swing-state Wisconsin, then flew home to Chicago to work on the acceptance speech he will deliver before 75,000 partisans on the convention’s closing night.

Previewing the week ahead, he said he hoped convention viewers would conclude, “He’s sort of like us. He comes from a middle-class background, went to school on scholarships. He and his wife had to figure out child care and how to start a college fund for their kids.”‘

Clinton outpolled Obama among working-class voters in many states through the winter and spring, and Sen. John McCain and the Republicans have worked relentlessly in more recent weeks to depict the Illinois senator as an elitist who is out of touch with blue-collar concerns.

With Democrats descending on their highly fortified convention city, party officials worked energetically to assure a harmonious week.

Thousands of blue signs that read simply “Unity” were stockpiled inside the Pepsi Center for distribution to convention delegates at whatever moment Obama’s high command deemed appropriate.

And on a unanimous vote, the party’s credentials committee restored full voting rights to delegations from Florida and Michigan. Both states were stripped of their voting rights earlier in the year in retaliation for holding primaries before party rules allowed.

The Democrats were meeting with public opinion polls giving Obama a modest advantage at best in the race to become the nation’s 44th president.

McCain has been on the political offense in recent weeks, and he has successfully cut into what had been a slightly more comfortable lead for the Democrat.

If Democratic unity was uppermost in the minds of Obama’s aides, McCain had other ideas.

The Republican presidential contender’s campaign readied a television commercial – there was no immediate evidence it had been broadcast – suggesting Obama had snubbed Clinton when he picked Delaware Sen. Joseph Biden as his vice presidential running mate.

“She won millions of votes but isn’t on the ticket. Why? For speaking the truth,” says the ad, which also shows Clinton criticizing Obama during their protracted battle for the Democratic presidential nomination.

The former first lady has praised Biden’s selection.