Two sources with direct knowledge of his plans told Yahoo News that Sanders, an independent and self-described “democratic socialist,” plans to announce his presidential bid imminently. While Sanders has been considering a bid for months, one of the sources said he was emboldened by early polls of the race that have consistently showed him as one of the top candidates in a crowded Democratic primary field. In particular, the source said Sanders was heartened to see numbers indicating he is one of the leading candidates among African American and Latino voters, two groups he was perceived as struggling with in 2016.

A third source said Sanders’ bid will begin with an exploratory committee. Sanders’ campaign did not immediately respond to a request for comment for this story.

In addition to these two sources, a former Sanders staffer who had not been briefed on the imminent announcement plans nevertheless said many recent signs suggest he is set to pull the trigger on a presidential campaign. Specifically, the former staffer said Sanders has been building out the infrastructure he would need for a White House bid.

“He’s already talking to staff and there are people he’s hiring. They’re nailing down contracts with vendors. … All the movement is there for him to run,” the ex-staffer said.