Former Vice President Joseph R. Biden Jr. is planning to create a political action committee, the most concrete sign yet that he intends to remain active in the Democratic Party and is considering a presidential bid in 2020.

The “American Possibilities” PAC, which Mr. Biden intends to unveil on Thursday, will offer the former vice president a platform he can use to nurture relationships with donors, travel on behalf of the party and contribute to candidates in the two governor’s races in November and in next year’s midterm elections.