WASHINGTON — Former President Bill Clinton is set to play a central part in the Democratic convention, aides said, and will formally place President Obama’s name into nomination by delivering a prime-time speech designed to present a forceful economic argument for why Mr. Obama deserves to win a second term.


The prominent role of Mr. Clinton, which is scheduled to be announced on Monday, signals an effort by the Obama campaign to pull out all the stops to rally Democrats when they gather for their party’s national convention in Charlotte, N.C. An even more important audience will be the voters across the country who will see the address carried by television networks.


“There isn’t anybody on the planet who has a greater perspective on not just the last four years, but the last two decades, than Bill Clinton,” David Axelrod, a top strategist to the Obama campaign, said in an interview on Sunday. “He can really articulate the choice that is before people.”


Vice President Joseph R. Biden Jr. will appear on the final night of the convention, making the case for Mr. Obama before the largest audience of the week during an outdoor speech at the Bank of America Stadium. The vice president and Mr. Obama will appear together on stage before they accept the party’s nomination for a second term in the White House.


It is unusual in recent election cycles, although not without precedent, for the vice president not to get the stage to himself during a night at the convention. But in his speech, aides said, Mr. Biden is expected to remind Americans about the last four years and the administration’s accomplishments in a difficult economic climate.


The invitation for Mr. Clinton to be center stage at the convention signifies another milestone in the complicated and evolving relationship between the two presidents.


At the party’s convention in Denver four years ago, all eyes were on Mr. Clinton as he offered a full-throated endorsement of Mr. Obama in a speech that served as something of a truce after a contentious primary fight with his wife.


For Mr. Clinton, who has become one of the most popular figures in the Democratic Party, the speech will be among the most high-profile roles yet that he has assumed for Mr. Obama. The address is intended to offer a strong contrast with the Republican ticket and will be closely watched, particularly given a string of blunt statements — and retractions — that Mr. Clinton has made this year when talking about the Obama administration.


For example, Mr. Clinton called for temporarily extending all of the tax cuts set to expire at the end of the year, including the Bush-era rates, which put him at odds with the president. He later apologized for those comments, but not before the Republican National Committee seized on the controversy.


Cheney on ’08 Palin Choice


Dick Cheney said on Sunday that Sarah Palin was not ready in 2008 to be his successor as vice president and that Senator John McCain’s decision was “a mistake” that Mitt Romney should seek to avoid making in his own choice of running mate.


Speaking to ABC News in his first interview since undergoing a heart transplant in March, Mr. Cheney said Mr. McCain’s choice clearly reflected considerations other than Ms. Palin’s ability to serve as vice president.


Asked whether a presidential candidate should consider how well a vice-presidential nominee might appeal in a particular state or to a demographic group, Mr. Cheney said, “Those are important issues, but they should never be allowed to override that first proposition.”