Vice President Joe Biden’s aides and supporters have intensified efforts in recent days to create a campaign-in-waiting, developing more detailed plans for staffing, fundraising and organizing as they prepare for a possible 2016 presidential bid.

Democratic fundraisers are working to recruit donors and lock down financial commitments. Mr. Biden’s aides are sketching out plans for potential hires in key primary states and considering which of the vice president’s longtime allies would work for a campaign and which would oversee a Biden super PAC.

The vice president has said he may not be ready to mount a bid for the White House, and people close to him say they are trying to give him the time and space to make a decision. But in private, Mr. Biden’s advisers and supporters are proceeding as if he soon could be running, underscoring a growing belief that a campaign launch remains a real possibility.