WRAPUP 6-Backers of Hillary Clinton cloud Obama show

* Obama promises "workmanlike" acceptance speech

* Michelle Obama disputes elitist charge

* Edward Kennedy to be honored

By Steve Holland,

DENVER, Aug 25 (Reuters) - Democrats opened their national convention on Monday and a rift involving Hillary Clinton's resentful supporters threatened to rain on presidential hopeful Barack Obama's nominating parade.

Democratic Party chairman Howard Dean pounded a gavel to open the four-day convention that Democrats say Obama must use to unite the party, draw a sharp contrast with Republican rival John McCain and back up soaring oratory with a policy for leading the country.

Obama tried to assuage anxiety among some Democrats about a mild slide in opinion polls that has left him in a dead heat with McCain heading toward the Nov. 4 election.

He said his nomination acceptance speech on Thursday would be "workmanlike," short on lofty words and long on policy details.

He also played down divisions with the former president and first lady.

"I am absolutely convinced that both Hillary Clinton and Bill Clinton understand the stakes," he told reporters in Moline, Illinois.

The day's agenda was focused on outlining Obama's personal story. In excerpts from her evening keynote speech, Obama's wife, Michelle Obama, seemed to want to dispel Republican criticism of Obama as an aloof celebrity.

"And in the end, after all that's happened these past 19 months, the Barack Obama I know today is the same man I fell in love with 19 years ago," she said.

Michelle Obama also tried to cast her own personality in a popular glow.

"I come here as a wife who loves my husband and believes he will be an extraordinary president. I come here as a mom whose girls are the heart of my heart and the center of my world," she said.

Democrats hoped a tribute to Massachusetts Sen. Edward Kennedy, a symbol of Democratic liberalism who is battling brain cancer, would bring the party together. An aide to Kennedy said the senator would attend but not speak.

Casting a cloud over the convention was ongoing resentment from supporters of New York Sen. Clinton, miffed that she lost the nomination and upset that she was not picked as Obama's vice presidential running mate. Obama chose veteran Delaware Sen. Joe Biden, who arrived at the convention on Monday.