Sanders wrote in an email sent to supporters Tuesday that he was building “an unprecedented and historic grassroots campaign” that would draw on people across the country.

“Our campaign is not only about defeating Donald Trump, the most dangerous president in modern American history. It is not only about winning the Democratic nomination and the general election,” he wrote. “Our campaign is about transforming our country and creating a government based on the principles of economic, social, racial and environmental justice.”

The senator, an independent, cited health care, climate change, student debt, the “demonization” of undocumented immigrants, income inequality, gun violence and the myriad problems of America’s needy as propelling him into his second presidential contest.