Tuesday is the second day of the convention which will nominate her husband, John Kerry.

Howard Dean, who had challeneged Mr Kerry in the Democrat primaries, spoke in support of his former rival.

"I'm proud of John Kerry's leadership, and I intend to stand shoulder to shoulder with him," said Mr Dean.

"This was never about me. It was about us. It was about giving new life to our party, new energy to our democracy," said the former governor of Vermont.

Ron Reagan, son of the late Republican president, is also due to speak, addressing delegates about the need for stem cell research.

Former President Bill Clinton launched a blistering attack on President George W Bush on the opening night on Monday.

He portrayed Mr Kerry as a Vietnam hero, ready to be a wartime leader.

But the latest poll suggested a decline in voter support for Mr Kerry.

Only 46% backed him against 48% for Mr Bush, said the Washington Post/ABC poll. Respondents said they did no know enough about Mr Kerry's policies.

The Democrat hopeful will address the convention on Thursday, its final day.

Teresa Heinz Kerry told CNN her speech would be "personal".

"It's my words. I feel very comfortable with it," Mrs Heinz Kerry said.

"I speak from my heart, from my head and from my soul."

Teresa Heinz Kerry brings an extraordinary range of experience and talent to the campaign trail for her husband. She has been deeply involved with a number of issues that are equally important to her husband, including the environment, children, women's issues, and health care and wellness. She has been an outspoken advocate for human rights, and a strong supporter of the arts.

Born in Mozambique, fluent in five languages, she has combined compassion and common sense to become a force for innovation and social progress as leader of one of the nation's largest private foundations. After studying in South Africa and Switzerland, she moved to the United States to work for the United Nations. In 1966, she married Senator John Heinz, with whom she had three sons. Shortly after celebrating their 25th wedding anniversary in 1991, she lost her husband in a plane crash.

Turning down offers to run for her husband's Senate seat, she became chair of The Howard Heinz Endowment and the Heinz Family Philanthropies. Under her leadership, the Heinz foundations are widely known for developing innovative strategies to protect the environment, improve education and the lives of young children, broaden economic opportunity, and promote the arts.

She started advocating for women early, attending the first meeting of the Women's Political Caucus in Pennsylvania in 1972. She established the Women's Institute for a Secure Retirement in 1996 to educate women about pensions, savings, and retirement security.

Their mutual interest in environmental issues brought Teresa and John together. She was first introduced to John Kerry by Senator Heinz at an Earth Day rally in 1990. In 1992, she ran into Kerry at the Earth Summit in Rio de Janeiro, where she was representing U.S. non-governmental organizations. In 1993 they began dating, and were married in the presence of her three sons and his two daughters on Memorial Day weekend in 1995.

Teresa has received numerous awards and 10 honorary degrees for her many works. In September of last year, she was presented with the Albert Schweitzer Gold Medal for Humanitarianism, for her work protecting the environment, promoting health care and education and uplifting women and children throughout the world. She was recently elected a fellow of the American Academy of Arts and Sciences.

In addition to her three sons and two step-daughters, Teresa is the almost inordinately (but understandably) proud grandmother of one grandchild.

Her son, Chris, is also due to address the delegates.

Mrs Heinz Kerry's speech is part of an attempt to improve the image of her husband.

But she has not done too well so far this week, says the BBC's Justin Webb at the convention.

She is uncontrollable, which in a pre-packaged political age, makes her unusually interesting, he says.

Mrs Heinz Kerry got into an argument with a journalist who had annoyed her on Monday.

A day later she was unrepentant.

"I fight and have fought and took risks for freedom, for justice and for fairness," Mrs Heinz Kerry told NBC television.

"If someone attacks me and my integrity and puts words in my mouth, I will defend myself, and I think every American person would too."

But she has caused further embarrassment with an interview conducted in the 1970s, unearthed by her enemies, in which she said she did not trust Edward Kennedy, now her husband's chief backer, our correspondent says.

In the interview she thought the Democrats were "putrid".

Senator Edward Kennedy is due to speak before the delegates on Tuesday - as well as former Vermont Governor Howard Dean - an early challenger of Mr Kerry for the Democratic Party nomination.