Progressive frontrunners face off at CNN debate which may also offer opening for centrists

CNN's first Democratic debate on Tuesday night will showcase a match-up between Sens. Bernie Sanders and Elizabeth Warren, two icons of the progressive movement who are ultimately on a collision course for the party's presidential nomination.

Their encounter will kick off two televised clashes between Democratic White House hopefuls on successive nights that could significantly reshape the primary campaign and will, for the first time, test how party hopefuls handle Donald Trump's ugly campaign strategy rooted in direct racism.

The debates, each featuring 10 candidates, mark the biggest moment of...