DES MOINES, Iowa (AP) — Hoping to revive his flagging bid for the Republican presidential nomination, former House Speaker Newt Gingrich is calling for an overhaul of the way Americans pay taxes and buy health care and would allow young people to opt out of the Social Security system.Gingrich said the 10-point plan he mapped out in a speech at a Des Moines insurance company would form the core of his campaign for the Republican presidential nomination. Key elements include repealing President Barack Obama's health care plan and giving taxpayers the option of paying a flat tax.He says voters this election are so worried about the condition of the country that they are demanding detailed solutions about how candidates would deal with those problems.