Richardson was Energy secretary and United Nations ambassador in the administration of President Bill Clinton. He sought the Democratic presidential nomination this year, but eventually dropped out and endorsed Mr. Obama.
He is one of the nation's most prominent Hispanic politicians, and was in the House before joining Mr. Clinton's Cabinet.
Democratic officials said Tuesday that Mr. Obama will join Richardson at a news conference in Chicago on Wednesday. They would speak only on condition of anonymity because the announcement hasn't been made.
A two-term governor of New Mexico, Richardson seemed to both relish the job, but also long for something more. Richardson's name was in the hopper as a possible vice president, then as secretary of state. Neither happened.
"I love my job (as governor). I'm not looking for a job," he said when asked shortly before the election whether he would accept a position in an Obama administration. But in recent weeks it also became clear that Richardson was not about to turn down a Cabinet assignment, even if secretary of state was out of the question.
Richardson, 61, boasts an extensive and wide-ranging resume. He has been described as a blend of East Coast establishment and Western individualism with a dash of Third World acumen. He combines a relentless competitiveness and political savvy with a jocular sense of humor and down-to-earth style that often tears down boundaries and disarms adversaries, associates say.
"His personality gets him in the door," says David Goldwyn, an associate of Richardson's at the United Nations. "From there he's got to deliver the message, he's got to be persuasive, and he's got to secure the objective. That's where the other part of his personality comes in - his relentlessness."
The Commerce secretary's job includes selling America to the international business community and dealing with trade issues.
As a seven-term congressman, Richardson showed a knack for freelance diplomacy, rushing off to such places as North Korea, Sudan, Cuba and Iraq on unofficial diplomatic missions. In 1995, he persuaded Iraqi President Saddam Hussein to release two American aerospace workers who had wandered into Iraq from Kuwait. He helped free three Red Cross workers in Sudan and mediated with North Korea over the downing of two U.S. Army helicopter pilots.
Richardson was disappointed when President Clinton passed him over for secretary of state. But in 1996, Mr. Clinton named him U.N. Ambassador. Two years later Clinton asked him to become energy secretary where Richardson was confronted almost immediately by an uproar over allegations of Chinese spying - later found to be untrue - and of a rash of security lapses at one of the government's premiere nuclear weapons labs at Los Alamos. Members of Congress criticized his handling of the matter, though many of the problems predated his arrival at the department.
In 2002, Richardson easily won election as governor of New Mexico, a state with a large Hispanic population and one he had represented in Congress for 14 years. He was re-elected in 2006 with 69 percent of the vote.
He continued to maintain a high national profile as chairman of the Democratic National Governors Association and by raising money for congressional candidates in the 2006 elections. And he sought to stake out positions on energy, land use, the environment and immigration.
Richardson was credited with helping to turn out the Hispanic vote for Mr. Obama. He would often switch between English and Spanish while campaigning. But he also lamented in an interview during his own presidential bid that because of his surname, many people didn't think he was Hispanic.
Born in Pasadena, Calif., Richardson's father was an international banker from Boston and his mother was Mexican. He lived his early childhood in Mexico City where his father worked for CitiBank. But as a teenager he attended an exclusive boarding school in Concord, Mass., and later earned a masters degree in international affairs from Tufts University.
He settled in New Mexico with politics on his mind. His first try at politics fell short, but he surprised political experts in 1980 - after only two years in the state - by coming within 1,000 votes of unseating veteran GOP Congressman Manuel Lujan.