WASHINGTON ?? Bitcoin hasn't yet become the currency of choice in federal political campaigns.Rep. Jared Polis, D-Colo., appears to be the only House member or candidate who has accepted the computer-generated currency since federal regulators first approved its use as political donations in early May, a USA TODAY analysis of new campaign reports show.Polis, an enthusiastic bitcoin backer, collected nearly $3,671 worth of bitcoin, the review of April-through-June reports shows.The Libertarian National Committee raised a little more than $2,300...