New presidential primary rules passed by the Democrat and Republican national committees are busting the bonds that made the 2008 “Potomac Primary” possible and threatening the Washington region’s clout in 2012. In 2008, Virginia, D.C. and Maryland all held their primaries on Feb. 12. It was just one week after “Super Tuesday,” when 24 states voted on presidential candidates. But there were no clear front-runners for the party nominations following the Feb. 5 votes, and the Washington region became key for Hillary Clinton and Barack Obama. Forming the Potomac Primary guaranteed the Washington region electoral pull.