“I wanted to let the people of the state of Vermont know about this first,” Sanders told VPR’s Bob Kinzel.
He is expected to make a video announcement later Tuesday morning.
The independent Vermont senator, who caucuses with the Democrats and battled Hillary Clinton for the Democratic presidential nomination in 2016, had long hinted he would make another run but said that he would step aside if a better candidate came forward to defeat President Donald Trump.
Sanders has long been known as one of the most progressive members of the Senate. A self-described democratic socialist, his platform calls for “Medicare for all” and a $15 minimum wage. He’s also advocated for free tuition at public colleges and universities, lowering the costs of prescription drugs and placing heightened attention on climate change.
Sanders won re-election to the Senate for a third term in November, taking more than 67 percent of the vote. That same month, he said he was considering a second White House run, but he told panelists on ABC’s “The View” that his primary objective was to defeat Trump, even if that meant the Democrats ran someone else.
“There are other great candidates out there, many of them personal friends of mine,” Sanders said during the November interview. “But what I think is most important right now is that Trump be defeated ... and that we as a nation come together respectfully.”
When he first announced he would run for president in 2015, Sanders was scoffed at as a fringe candidate. By the end, Sanders had proved to be a national political force, amassing an army of loyal followers and unprecedented amounts of small-donor fundraising money. When all was said and done, he had won more than 1,800 delegates.
In recent months, that same campaign has faced criticism, however, after two dozen women came forward with allegations that they were subjected to harassment or discrimination by members of Sanders’ team. The senator issued a public apology to those who experienced such harassment and thanked them for speaking out.
“What they experienced was absolutely unacceptable and certainly not what a progressive campaign, or any campaign, should be about,” he said in a Jan. 10 statement.
There are also concerns about Sanders’ age. He would be 79 on Election Day in 2020, which would make him the oldest president elected in U.S. history.
Nevertheless, Sanders has continued to poll favorably among Americans over the last two-plus years.
The Harvard Harris poll, which releases its findings monthly, has repeatedly named him the most popular active politician in the country. Poll results from both January and December placed him among the three most favored political figures in the country, just behind former President Barack Obama and former Vice President Joe Biden, who is also eyeing a presidential run.
This is a developing story. Please check back for updates.