Biden, the Democratic vice president, and Ryan, the Wisconsin congressman and Republican vice presidential nominee, will square off Thursday at Centre College in Danville, Ky.
The Pew Research Center for the People & the Press said one of its polls found Biden is viewed favorably by 39 percent of registered voters and 44 percent look kindly on Ryan.
The favorability poll of 1,511 adults, including 1,201 registered voters, was conducted nationwide Oct. 4-7.
In a separate poll of 1,006 adults, including 812 registered voters, conducted during the same time period, 40 percent said they think Ryan will do a better job in the debate, while 34 percent think Biden will win.
Pew found 35 percent of independent voters have a favorable opinion of Biden and 42 percent think favorably of Ryan, and independents give the debate edge to Ryan by a 42-35 margin.
Only 54 percent of those surveyed said they will watch the vice presidential debate.
The margins of error range from 2.9 to 4.1 points.