Vermont Senator Bernie Sanders will announce his plans to seek the Democratic nomination for president on Thursday, presenting a liberal challenge to Hillary Clinton, The Associated Press (AP) reports.

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 AP 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 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 Senator Elizabeth Warren to join the race, noted AP.

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.

Sanders, who is Jewish, recently made headlines when he became the first senator to announce he would not be attending Prime Minister Binyamin Netanyahu’s speech before Congress.

“The president of the United States heads up our foreign policy. The idea that the president wasn’t even consulted — that is wrong and not a good thing for our country,” Sanders said at the time, referring to the fact that House of Representatives Speaker Republican John Boehner invited Netanyahu to make the speech without the knowledge of either the White House’s or Democratic leaders in Congress.

“I’m not thinking about it. I’m not going. I may watch it on TV,” Sanders stressed.