President Barack Obama Thursday night laid out his case for being re-elected to a second term by comparing himself to Franklin D. Roosevelt, who won an unprecedented four presidential elections and led America to recovery after the Great Depression.

The speech came as Obama and Romney were deadlocked in the national opinion polls in a race that has been too close to call for many months. It was the last opportunity for either man to use a defined 'moment' to change the trajectory of the race before the three presidential debates in October.

In a sometimes dour and hard-edged address in Charlotte, Obama used his speech accepting the Democratic nomination to launch sarcastic attacks on Republicans as the party of the wealthy and even mocked his opponent Mitt Romney for a slip in an eve-of-Olympics interview in London that affronted some Britons.