Vermont Sen. Bernie Sanders will announce his plans to seek the Democratic nomination for president on Thursday, presenting a liberal challenge to Hillary Rodham Clinton.
Sanders, an independent who describes himself as a "democratic socialist," will follow a statement with a major campaign kickoff in his home state in several weeks. Two people familiar with his announcement spoke to The Associated Press under condition of anonymity to describe internal planning.
Sanders will become the second major Democrat in the race, joining Clinton. He has urged the former secretary of state to speak out strongly about issues related to income inequality and climate change. The former first lady and New York senator is viewed as a heavy favorite in the primary and entered the race earlier this month.
The white-haired senator and former mayor of Burlington, Vermont, has been a liberal firebrand, blasting the concentration of wealth in America and assailing a "billionaire class" that he says has taken over the nation's politics. His entry could be embraced by some liberals in the party who have been disenchanted with Clinton and have unsuccessfully urged Massachusetts Sen. Elizabeth Warren to join the race.
In recent weeks, Sanders has been a forceful critic of the proposed Trans-Pacific Partnership trade agreement, which would eliminate tariffs and other trade barriers for the U.S., Canada and Asian countries conducting commerce with each other.
"One of the key reasons why the middle class in America continues to decline and the gap between the very rich and everyone else is growing wider is because of disastrous trade agreements which have sent millions of decent-paying jobs to China and other low-wage countries," Sanders said last week.
Sanders generated attention in 2010 when he staged a lengthy Senate floor speech opposing a tax agreement by President Barack Obama and Republicans.
He has called for universal health care, a massive infrastructure jobs and building program, a more progressive tax structure and reforms to address the Supreme Court's Citizens United decision, which Sanders says has unleashed a torrent of money from big donors to political candidates.
The senator has generated some enthusiasm on college campuses and liberal enclaves in the early voting states of Iowa, New Hampshire and South Carolina and made several trips to court the influential Democratic voters there.
"He will add color," said Lou D'Allesandro, a Democratic state senator from New Hampshire. "He's not bashful about anything."
Kathy Sullivan, a New Hampshire supporter of Clinton and a member of the Democratic National Committee, said Sanders' decision was expected.
"I know Hillary Clinton has always been expecting for there to be a competitive Democratic primary in New Hampshire," Sullivan said. "I think he should be taken seriously."
Karl Rhomberg, a Davenport, Iowa, Democratic activist, said that while he expects Clinton "to be the nominee, I expect her to listen to Bernie, listen to (Martin) O'Malley and listen to people from the left." He added: "If Bernie is going to put a stake on the left side of the field and draw Hillary toward it, that's OK with me."
Sanders will start his campaign as a distinct underdog against Clinton, who remains the dominant front-runner. The Vermont senator is likely to face other challengers in the primary, such as O'Malley, the former Maryland governor, former Virginia Sen. Jim Webb and ex-Rhode Island Gov. Lincoln Chafee.
A feisty voice for liberal policies, Sanders has long championed working-class Americans. He grew up in a Jewish family in Brooklyn - his father, an immigrant from Poland, sold paint for a living -and his views about the distribution of wealth were formed early.
"A lack of money in my family was a very significant aspect of my growing up," Sanders told the AP in December. "Kids in my class would have new jackets, new coats, and I would get hand-me-downs."
After his graduation from the University of Chicago, Sanders moved to Vermont in the 1960s as part of the counterculture, back-to-the-land movement that turned the state from solid Yankee Republican into one of the bluest in the country.
Sanders lost several statewide races in the 1970s before he was elected mayor of Burlington in 1981 - a race he won by 10 votes. He was elected to the House a decade later, then won a Senate seat in 2006. He has carried a consistent message during his political career, arguing that the system is rigged in favor of the wealthiest Americans to the disadvantage of the nation's poor and working class.