WASHINGTON, Oct. 5 - National Republicans, who face an uphill battle in their efforts to capture the open United States Senate seat in heavily Democratic Maryland next year, are trying to exploit potential legal problems that Democrats are now suddenly facing in that race. The Republicans are seizing on a disclosure that two researchers at the Democratic Senatorial Campaign Committee improperly obtained the credit report of Lt. Gov. Michael Steele, a Republican who is considering a bid for the Senate seat. In recent days, Republicans have sought to put Democrats on the defensive, saying the incident underscores just how concerned...