Ilhan Omar is greeted by fans last week after she and Rashida Tlaib, Alexandria Ocasio-Cortez and Ayanna Pressley were attacked by Donald Trump

Whether it is casinos, skyscrapers or hotels, Donald Trump has always been a gambler. Now he is betting his entire political future on the most corrosive issue in American public life: race.

The bitter controversy that Trump ignited last Sunday — when he suggested that four left-wing congresswomen “go back” to the countries from which they came — has grown into one of the defining moments of his presidency.

By Wednesday evening, the crowd at Trump’s rally in Greenville, North Carolina, were chanting “send her back” about Ilhan Omar, a Somalian-American congresswoman who came to the US as a child refugee. Trump did nothing to discourage them. It was a moment that shocked America and drew widespread condemnation from world leaders.

Trump’s gamble is this: