CONCORD, N.H. (AP) — Mitt Romney says the nation's credit problem arose because President Barack Obama has failed to show leadership on the economy.The Republican presidential contender tells the Concord Chamber of Commerce in a New Hampshire campaign appearance that Obama must do more to restore the nation's credit rating. Standard & Poor's downgraded it late last week.Romney called the downgrade a wakeup call. The former Massachusetts governor described Obama's leadership, in his words, as "a blame presidency." And Romney says the president must reach across the aisle and stop bashing his political opponents.Romney did not say what he would have done differently. Instead, he repeated support for the so-called cut, cap, and balance plan backed by congressional Republicans that was abandoned because it couldn't win enough Democratic votes.