WASHINGTON — Just as Democrats were starting to count him out, Joe Biden sent a clear signal through his political team that not only might he enter the presidential race soon, he has a strategy prepared that he thinks could win.

After months of growing calls for him to run, the vice president’s tide began turning this week after the first Democratic debate, which softened concerns about front-runner Hillary Rodham Clinton while obscuring any obvious rationale for Biden to run. But in a letter to former Biden staffers late Thursday, one of Biden’s closest advisers traced the contours of the argument Biden would make, and suggested a decision to run could be imminent.

“If he runs, he will run because of his burning conviction that we need to fundamentally change the balance in our economy and the political structure to restore the ability of the middle class to get ahead,” former Sen. Ted Kaufman said in an email to a list of “Biden alumn.” The letter was obtained by The Associated Press.

Kaufman, who served as Biden’s chief of staff for two decades before replacing him in the Senate, has been at the vice president’s side for months, brought back into the immediate fold after Biden’s son died in May. He and two other aides have formed a protective and tight-lipped ring around Biden as he ponders a 2016 campaign.

“If he decides to run, we will need each and every one of you — yesterday,” Kaufman said, alluding to the breakneck speed at which Biden would have to ramp up a campaign after waiting this long to enter. Kaufman said he was confident Biden understood “the practical demands of making a final decision soon.”