President Obama will use his election-year State of the Union address on Tuesday to argue that it is government’s role to promote a prosperous and equitable society, drawing a stark contrast between the parties in a time of deep economic uncertainty.

In a video preview e-mailed to millions of supporters on Saturday, as South Carolina Republicans went to the polls to help pick an alternative to him, Mr. Obama promised a populist “blueprint for an American economy that’s built to last,” with the government assisting the private sector and individuals to ensure “an America where everybody gets a fair shot, everyone does their fair share and everybody plays by the same set of rules.”

Mr. Obama has honed that message for months as he has attacked Republicans in Congress and on the presidential campaign trail, contrasting it with what he has described as Republicans’ “go it alone” free-market views.