Left-wing Democrats are on a winning run - but can they lure back crucial swing voters?

On a Saturday evening in Michigan, the skies still hazy from drifting Canadian wildfire smoke, hundreds of voters packed into Detroit's opulent 104-year-old Opera House, rising from their seats to cheer loudly as Senator Bernie Sanders and Democratic Representative Alexandra Ocasio-Cortez took the stage. As two of the leading figures on the American left, Ocasio-Cortez and Sanders were there to champion Senate hopeful Abdul El-Sayed - a doctor running on a platform of universal healthcare.His supporters carried signs with El-Sayed's slogan "Medicare for All", and wore shirts urging the end of immigration enforcement and US aid to Israel.But they were not the only ones tuning in. Voters and politicians across the country are watching to see if El-Sayed can earn the Democratic nomination to run for Senate in November's midterm elections. His opponent - Congresswoman Haley Stevens - is an experienced politician with deep pockets, thanks in part to large corporate campaign donations.The two represent the divisions within the Democratic Party as it seeks to take back control of Congress. On one side is the centrist establishment, backed by traditional power players. On the other is the ...