[Johnny-come-lately] {n.} Someone new in a place or group;newcomer; also: a new person who takes an active part in group affairsbefore tlie group has accepted him; upstart.

Everybody was amazedwhen a Johnny-come-lately beat the old favorite in the race.

Whenit looked as though Mr. Brown had a good chance of winning, manyJohnny-come-latelies began to support him.