What is the word/phrase that describes a situation at which between 2 sides, it is hard to decide which side will win? For example, in football, when 2 teams are competitive but cannot get out of a draw, and maintain at that situation.
Two people or teams who are evenly matched are equally good, or have an equal chance of winning.
If two opponents, whether in sports or an election, are evenly matched or polling suggests close result, then it's called a tossup or, still retaining the hyphen, toss-up.
If the outcome is predicted to be very close, one might call it a race to a photo finish. The term comes primarily from horseracing before extremely precise timekeeping devices, where a photograph was used to determine which horse's nose was first over the finish line.
The American electorate has a fundamental tendency to divide closely, with "photo finish" elections being almost the rule rather than the exception.