In a year of liberal challenges to President Donald Trump, an avowed centrist scored the Democratic Party’s biggest coup -- flipping a red state’s U.S. Senate seat.

Voters in Colorado have elected the country's first openly gay governor. Rep. Jared Polis defeated Republican state Treasurer Walker Stapleton to keep the governor's seat in Democratic hands.

The battle for Senate control finds Democrats trying to mount upset challenges in a string of typically Republican states, and this round of Battleground Tracker polls shows them having at best mixed results so far.