a one horse race
a competition which one particular person or team is very likely to win because they seem much better than the other people competing
one horse race
a race, competition which a particular person or thing looks likely to win easily

[TahlilGaran] Dictionary of Contemporary English ▲

a one-horse race
a competition which one particular person or team is very likely to win because they seem much better than the other people competing.
This election has been a one-horse race right from the start.

[TahlilGaran] English Idioms Dictionary ▲