evidence: The vice-president, who launched her presidential campaign earlier this week after President Joe Biden announced his decision to exit the race, is traveling to Indianapolis for a previously scheduled event and will be unable to preside over the prime minister's congressional address. [...] While President Biden's decision to abandon the race is unusual, it is not unprecedented. Fifty-six years ago, President Lyndon B Johnson announced he was giving up his bid for re-election on 31 March 31 1968. [...] Speaking to campaign staffers via phone, Biden said leaving the race was the "right thing to do".