TAMPA, FLORIDA -- New Jersey Governor Chris Christie promised a return to American greatness and leadership in the world during his keynote speech at the Republican National Convention Tuesday."Tonight we are doing what is necessary to make America great again," Christie said in a rousing address on the first full day of the convention, which was supposed to start Monday but was delayed due to a tropical storm."Standing strong for freedom will make this century as great as the last one," he told the cheering Republican delegates, who jumped to their feet throughout his appearance.He evoked the memory of the "greatest generation" of World War II veterans who succeeded in "fighting Nazi tyranny" in calling on Americans to overcome the country's current challenges.Christie took the stage after Mitt Romney's wife Ann spoke to the audience about her husband, telling them they first met at a high school dance.Convention-goers flashed signs proclaiming "We love Ann" and several times broke into chants communicating the same message.The brief appearance was the first at the convention for Mitt Romney, who had only originally been announced to appear only when accepting the party's nomination on Thursday night.Republican governors, small business owners and members of Congress proceeded Christie and the Romneys on the convention stage Tuesday night, repeatedly criticizing Obama's handling of the economy and his vision for government and spending.In contrast, foreign policy was hardly mentioned from the convention podium, with a lone remarks about Israel and its importance as an American ally made by a Republican candidate for Congress earlier on in the day.Rabbi Meir Soloveichik, however, opened Tuesday's proceedings with an invocation that referenced Israel and its importance as a beacon of democracy and hope. On Wednesday, a Sikh leader will offer the invocation. He will be followed by a video featuring Ron Paul -- who lost his bid for the Republican nomination to Romney but still has many adherents at the convention -- and a speech by his son Rand Paul, a Kentucky senator.Arizona Senator John McCain, who was the Republican nominee in 2008, is also scheduled to address the RNC Wednesday, as is former secretary of state Condoleezza Rice. The key address of the evening, however, will be delivered by vice presidential pick Paul Ryan.Like many other speakers, she poked at US President Barack Obama's rhetoric and campaign promises. In a reference to Obama's recent comments that American entrepreneurs build their businesses with help from others, Ann Romney said of the business that Mitt started: "Mitt Romney was not handed success. He built it."The line received a huge amount of applause from the crowd, which was later rewarded with an appearance by Mitt Romney himself to escort his wife off the stage.