"Energy security will revitalize rural America, re-establish our moral leadership on global warming and climate security and eliminate our addiction to foreign oil," said Vilsack, a prominent proponent of ethanol, biodiesel and wind power.
"In the past eight years, I have led our state of Iowa into successfully changing farm fields into energy fields," Vilsack told a gathering of supporters in the small town where he got his start in politics as mayor. "We changed the traditional idea of agriculture and became the national leader in renewable fuel and energy production."
Vilsack, 56, is not exactly a political household name, reports CBS News correspondent Peter Maer, but he clearly hopes to change that as he becomes the first Democrat to enter the race.
Earlier this month, he established a presidential campaign committee, giving him an early start on fundraising. He raised more than $6 million for his 2002 re-election bid, but that is just a fraction of the estimated $20 million political experts say presidential candidates will need to have in hand by June 2007.
The election will be the first in 80 years in which neither a sitting president nor vice president is in the early mix of candidates of either party.
Of the potential Democratic contenders, Sens. Hillary Rodham Clinton of New York and Barack Obama of Illinois are the best known. Other possible candidates include Sens. Evan Bayh of Indiana, former North Carolina Sen. John Edwards and New Mexico Gov. Bill Richardson.
Among Republicans, Sen. John McCain of Arizona, Massachusetts Gov. Mitt Romney and former New York City Mayor Rudy Giuliani are the most prominent.
Vilsack, who is finishing his second term as governor, has carved out a reputation as a centrist — balancing his state's budget and refusing to raise taxes, while emphasizing increased spending on such priorities as education, health care and higher wages. He chairs the Democratic Leadership Council, the party's signature centrist group.
"We have president whose first impulse is divide and conquer, who preys on insecurities and fears for partisan gain ...," Vilsack said, going on the offensive against President Bush.
"America needs a president who builds and creates, who makes our country more secure, who is bold and has the courage to create change," Vilsack said. "I will be that president."
After his announcement, Vilsack planned a five-state tour of several early voting states, including New Hampshire, South Carolina and Nevada.
Renewable energy proposals are likely to play well in Nevada, whose vast stretches of open land, abundant sunshine and geothermal resources are viewed by many as largely untapped energy potential to feed a growing population.
Vilsack has a compelling personal story he hopes will spur national interest in his candidacy. He was left as an infant at a Catholic orphanage in Pittsburgh. He was adopted by a well-to-do couple, but his adoptive mother was an alcoholic who beat him and his adoptive father struggled with financial reversals.
"I began life in an orphanage in the hands of a stranger. I was adopted into a loving but troubled home," Vilsack said. "I know what it is like to feel alone and to feel as if you do not belong."
Though Vilsack remains popular with Democrats in his home state, rivals have made it clear they won't cede Iowa's Democratic caucuses — a potential springboard to the nomination — to Vilsack.
The governor said he expects a spirited race. A poll last summer showed Vilsack running fourth in the state among potential Democratic candidates.