Mitt Romney did some of what he needed to do, but not everything he needed to do, at the Republican convention that ended Thursday night. In three days, he united and excited the conservative base through a tough, well-received speech by Rep. Paul Ryan; avoided any serious demonstrations, floor fights or mistakes (except for Clint Eastwood); and gave an acceptance speech that gave new and even endearing glimpses of his personal history. But what he didn't do was make a positive case for himself and whatever real plan he has for economic growth. He once again underscored that his main argument is not that he has a real plan to succeed but that President Barack Obama has failed.