Representative Chris Van Hollen of Maryland, the top Democrat on the House Budget Committee, has emerged as the choice to play Representative Paul D. Ryan in mock debates with Vice President Joseph R. Biden Jr.
People familiar with the planning said that Mr. Van Hollen, who has spent many hours with both Mr. Ryan and his budget plan, was being lined up for the role-playing in advance of the Oct. 11 debate in Danville, Ky.
The selection of Mr. Ryan, the voice of conservative House Republicans on fiscal issues, as the Republican vice-presidential candidate has raised interest in the coming rhetorical showdown given Mr. Biden's affinity for saying what he is thinking and Mr. Ryan's own confidence in his positions and his eagerness to articulate them.
Mr. Van Hollen's budget expertise and familiarity with Mr. Ryan made him a natural pick as someone who could give Mr. Biden a taste of what he could expect from his debating rival.
Mr. Van Hollen has quickly emerged as a leading surrogate for the Obama campaign on budget issues. On Wednesday, he traveled to New Hampshire for a speech lacing into the fiscal proposals of Mr. Ryan and his running mate, Mitt Romney.
Senator John Kerry of Massachusetts was earlier identified as the person who will stand in for Mr. Romney for President Obama's debate practices, setting up a faux Kerry-Van Hollen ticket.
