"Political capital is a metaphor used in political theory to conceptualize the accumulation of resources and power built through relationships, trust, goodwill, and influence between politicians or parties and other stakeholders, such as constituents." Wikipedia
Each rally POTUS does builds political capital. Reagan worked hard building his political capital, but nowhere as hard as Trump. In his second two years in office, his growing political capital will allow him to accomplish a lot more in his second two years. All we have to do to insure that is vote.