Hundreds of thousands of people marched through Madrid on Saturday in a show of strength by a fledgling radical leftist party, which hopes to emulate the success of Greece's Syriza party in the Spanish general election later this year. Podemos supporters from across Spain converged around the Cibeles fountain Saturday before packing the avenue leading to Puerta del Sol square in what was the party's largest rally to date. State broadcaster TVE said that hundreds of thousands were at the march, but no official attendance figures were provided. Podemos ("We Can") aims to...