President Donald Trump launched his 2020 reelection campaign Tuesday, whipping up a crowd of at least 20,000 with a nationalist boast about the United States (US) economy being the "envy" of the world and warning that opposition Democrats want to "destroy" the country.Promising the packed arena in Orlando, Florida an "earthquake at the ballot box," Trump said: "We did it once and we're going to do it again – and this time we're go