Donald Trump has made supporters at the Republican convention in Dallas take a pledge of allegiance to what he called the ‘greatest president in history’ or risk ‘going to hell’. The US president also repeated his promise to give every American adult $5,000 if his party wins the midterms in November, and kept invoking the threat of ‘communism’ if the Democrats take power. But Trump’s approval ratings have been steadily falling. Our North America Correspondent Jon Brain reports from Dallas.