U.S. Democrats back on campaign trail after third presidential debate

FILE PHOTO: Former Vice President Joe Biden speaks as South Bend Mayor Pete Buttigieg, Senator Bernie Sanders, Senator Elizabeth Warren and Senator Kamala Harris listen during the 2020 Democratic U.S. presidential debate in Houston, Texas, U.S., September 12, 2019. REUTERS/Mike Blake/File Photo

HOUSTON (Reuters) - The Democratic presidential contenders head back to the campaign trail on Friday after a debate that reinforced former Vice President Joe Biden's front-runner status and left his rivals searching for a formula to knock him out of the top spot.

The candidates who participated in Thursday's debate in Houston, and those scrambling to try to qualify for next month's debate in Ohio, have less than five months to plead their case to voters before the first nominating contest in Iowa on Feb. 3, 2020.