No matter what help Barack Obama might get from Sen. Joseph Biden, his newly named vice presidential running mate won’t give Obama much cover on the Tony Rezko front.

Biden has described himself as a 30-year friend of a key figure in the Rezko trial who’s pleaded guilty to a federal extortion charge in Chicago and is awaiting sentencing.

When the Delaware senator began contemplating his own 2008 presidential run, he initially was helped by Chicago lawyer Joseph Cari Jr., who also served as Biden’s Midwest field director in his failed 1988 bid for president.