The Wisconsin Congressman will spar with Mr Obama’s deputy, Joe Biden, over domestic and foreign policy in a 90-minute debate at Centre College in Danville, Kentucky.
While the 42-year-old is a far less experienced politician and debater than his 69-year-old opponent, who became a US senator in 1973 when Mr Ryan was only two, experts say his performance is crucial to sustain the boost in popularity Mr Romney gained by besting Mr Obama in the first presidential head-to-head a week ago.
“The Obama campaign has lost all the momentum they had and now are in danger of falling behind,” said Matthew Down, a former senior adviser to president George W Bush now a political analyst for ABC News.
“Biden is important to stop the bleeding and regain their footing. And as important, Ryan has to not step in it, so the Romney trajectory can continue.”
Just days after trailing the Democrats by more than three points in a Rasmussen tracking poll, the Romney campaign is now ahead by one, his first lead of the year, according to yesterday’s figures, although the margin of error makes it an effective dead heat.