CHARLOTTE, N.C. -- President Barack Obama's campaign moved aggressively Sunday to cast GOP vice presidential pick Paul Ryan as outside the mainstream, while Republicans relished in Mitt Romney's embrace of a running mate with solid conservative credentials. David Axelrod, Obama's senior campaign adviser, tagged Ryan as a "right wing ideologue" who wants to convert Medicare into a voucher plan and put the popular health-care program for the elderly in "a death spiral." Republicans heaped praise on Ryan, a Wisconsin congressman, for taking on tough decisions facing the economy and entitlement programs.