WASHINGTON — While Senator Clinton is presenting her long-awaited plan for universal health care today, her chief rival for the Democratic presidential nomination, Senator Obama of Illinois, will be in the heart of her home state, delivering a speech on the economy at the Nasdaq market in Times Square.

Mr. Obama’s campaign says he will lay out a broad economic vision in his speech today before issuing a set of proposals in an address tomorrow at the Tax Policy Center in Washington.

The first-term senator has yet to outline a comprehensive economic platform, although proposals he has made to date offer a glimpse into his likely agenda. To pay for his health care plan, Mr. Obama has said he would scrap President Bush’s tax cuts for Americans making more than $250,000 a year when they expire in 2010, and he has backed more than doubling the tax rates for managers of hedge funds and private equity firms.

While a campaign spokeswoman said Mr. Obama’s appearance this morning at the Nasdaq Marketsite had been scheduled for weeks, he will be competing with Mrs. Clinton, who is detailing her proposal for universal health coverage in Iowa.

Later today, both Mrs. Clinton and Mr. Obama, along with the other Democratic presidential hopefuls, will be addressing a major Washington conference of the Service Employees International Union, the 1.9 million-member labor organization.

A detailed health proposal from Mrs. Clinton has been widely anticipated. She has been promising a plan for universal coverage at nearly every turn since announcing her candidacy in January, and those pledges have often come with a self-deprecating quip about the “scars” she keeps from her first, failed attempt to insure all Americans when she served as first lady in 1993–94.

Mrs. Clinton has tried to use her unsuccessful bid during her husband’s administration as a badge of honor, touting her experience on the issue and saying it taught her key lessons about the need to build consensus. But her Democratic rivals have not let her off so easily, suggesting she is far from blameless and criticizing her for not renouncing the industry lobbyists in Washington who they say are stifling attempts at reform.

On the other side, Republican candidates have characterized Democratic health insurance plans in nearly apocalyptic terms, saying they will lead to “socialized medicine” and ruin America’s reputation for providing the highest quality health care in the world.

Mr. Obama and John Edwards of North Carolina each offered detailed plans months ago to cover the estimated 47 million uninsured, and their campaigns fired warning shots yesterday in advance of Mrs. Clinton’s proposal. A spokeswoman for Mr. Obama said his plan went further in reducing costs than either Mrs. Clinton or Mr. Edwards, and that he was the only candidate who “had the ability to bring people together to find common ground.”

“Unless we have a leader that can bring different groups together to lead a transparent, open process and find areas where we can agree, the special interest groups and insurance companies are going to defeat any reform efforts like they did in 1994,” the spokeswoman, Jennifer Psaki, said.

An Edwards spokeswoman, Colleen Murray, said the former senator was the only candidate with “the courage” to completely shut out lobbyists and be “honest” about the cost of achieving universal coverage. Mr. Edwards routinely says he will need to raise taxes to pay for his plan, and he has challenged his opponents to do the same.

He has also criticized Mr. Obama for not including a full mandate to require individuals to have insurance. Mr. Obama’s plan only mandates coverage for children. While Mrs. Clinton’s campaign was tight-lipped yesterday about specifics, her plan is expected to include a coverage requirement for both children and adults.

Mr. Edwards will also try to preempt Mrs. Clinton’s roll-out; his campaign said last night that he planned to make a “major announcement” about his strategy for achieving universal coverage during a speech to labor leaders this morning in Chicago.