DENVER — Republicans today invoked Senator Clinton’s past criticism that Senator Obama wasn’t ready to lead as Democrats faced two days at their national convention to be dominated by the old Clinton regime.

Mrs. Clinton, Mr. Obama’s former rival for the nomination, was expected to urge her disappointed supporters to line up in unity behind Obama in a prime-time speech to the Democratic National Convention. Her husband, President Clinton, speaks to the convention on tomorrow night.

Some Democratic activists, meanwhile, voiced concern that the convention, which began yesterday, had yet to produce a sustained or effective attack against Senator McCain.

In particular, they cited comments by Virginia Governor Mark Warner, who also was to address the convention tonight, suggesting that his speech would not be a red-meat attack on Mr. McCain but an appeal for bipartisanship.

“There may be parts of the speech that aren’t going to get a lot of applause, but I’ve got to say what I believe will get out country back on the right path,” Mr. Warner told reporters yesterday.

A democratic strategist, Paul Begala , took issue with Mr. Warner’s comments, suggesting that more partisanship, not less, is needed at the party convention.

“This isn’t the Richmond Chamber of Commerce,” Mr. Begala said today.

Yesterday James Carville, who managed Bill Clinton’s successful 1992 campaign, told CNN: “If this party has a message, it’s done a hell of a job hiding it tonight, I promise you that.”

The day Mrs. Clinton was to address the convention, Mr. McCain’s latest TV ad played off her primary campaign spot featuring sleeping children and a 3 a.m. phone call portending a crisis. In the new ad Clinton is shown saying: “I know Senator McCain has a lifetime of experience that he will bring to the White House. And, Senator Obama has a speech he gave in 2002.”

A narrator adds: “Hillary’s right. John McCain for president.”

Mrs. Clinton has already denounced such tactics. “I’m Hillary Clinton and I do not approve that message,” she told members of the New York delegation yesterday.

Meanwhile, Mr. McCain is expected to name his running mate in the coming days.

A top surrogate and prospective No. 2, Governor Mitt Romney was to be in Denver today to assail Democrats on behalf of Mr. McCain. It amounted to a final audition of sorts as Mr. McCain seeks a strong running mate who can play the attack-dog role against Mr. Obama and running mate Joe Biden. Another Republican said to be a serious vice presidential contender, Minnesota GovernorTim Pawlenty, was scheduled to be in Denver doing the same on Thursday.

Mrs. Clinton once seemed to have the nomination in her grasp and now is being called on to defend and support the person who wrested it from her. She is effectively playing middlewoman tonight — passing a torch from her husband, the 42nd president, to Mr. Obama, who wants to succeed him as the next Democratic president.

But not without some Clinton-style political dealmaking and drama.

The Clinton and Obama camps agreed to limit tomorrow’s divisive nominating process for president, allowing some states to cast votes for both Obama and Clinton before ending the roll call in an acclamation for the Illinois senator.

In one scenario, Mrs. Clinton herself would cut off the voting and urge the unanimous nomination of Mr. Obama, according to Democratic officials involved in the negotiations. They discussed the deal on condition of anonymity while final details were being worked out.

But some Clinton delegates said they were not interested in a compromise, raising the prospect of divisive floor demonstrations.

“I don’t care what she says,” a Maryland delegate who wants to cast a vote for Clinton, Mary Boergers, said.

“There is no doubt in anyone’s mind that this is Barack Obama’s convention,” Mrs. Clinton told reporters. And yet, she said, some of her delegates “feel an obligation to the people who sent them here” and would vote for her.

As part of the deal, Obama and Clinton activists teamed up and circulated three petitions on the convention floor last night — supporting Mrs. Clinton, Mr. Obama and his running mate, Joe Biden. Each needed 300 signatures.

Mrs. Clinton said she wouldn’t tell her backers how to vote, but she told them she would cast her own vote for Mr. Obama.

As well as Mrs. Clinton’s speech, the lineup for the second day of the convention features 11 governors and prominent House and Senate leaders. The convention’s keynote address will be given by Mr. Warner, a former Clinton supporter.

The Clintons will dominate the next two days of the convention, just as they have dominated Democratic politics for the past 16 years

This morning, Mr. Clinton was participating in a panel at the Club of Madrid NDI International Affairs Forum “to discuss ways in which his foundation is addressing some of the world’s most pressing problems,” his spokesman, Matt McKenna, said.

The former president planned few other public outings, and no news media appearances.

“President Clinton understands this is Senator Obama’s convention and he is here to do all he can to make Senator Obama our next president,” McKenna said in an e-mail message.

Asked whether the Clintons’ star power could eclipse Mr. Obama during his moment in the sun, House Speaker Nancy Pelosi said, “Absolutely, positively not.”

“We’re talking about the nominee for the president of the United States,” she said.

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Associated Press writers Liz Sidoti, Nedra Pickler, Charles Babington and Stephen Ohlemacher contributed to this story.