At one stage in this election cycle, Sen Marco Rubio of Florida was considered a heavy favourite to win re-election to a third term.
A well-known incumbent and former presidential candidate, Mr Rubio was running in a state that has trended Republican in recent years in an election that appeared to be shaping up promisingly for Republicans around the country. His seat, compared to seats in states like Wisconsin and Pennsylvania, was not thought to be a prime Democratic pickup opportunity.
