This word "forerunner" is the Greek prodromos, used in Scripture only this one time. It means "scout," "guide," or "one sent before a king to prepare the way." The Greeks also used prodromos to mean "firstfruits."
In the story of Daniel Boone, he went first to scout out Kentucky, then later took a party of thirty woodsmen to improve the trail, and after that, even more people followed. Boone was the forerunner, but so were those who went with him to develop the route. That first small group was the firstfruits. Spiritually, Christ has gone ahead, showing us the way, and we, as the firstfruits, improve the trail so that others will someday walk it more easily.
The concept of a forerunner runs throughout the Bible. We could say that Adam was a forerunner, as well as Noah, Abraham, Moses, Elijah, John the Baptist, and of course, Christ. Notice that each of these forerunners had followers—their firstfruits. Adam had Eve and their sons and daughters that followed them. Noah had his wife and family. Abraham had Sarah and Lot, and later were added Ishmael and Isaac, and then Jacob and his children. Moses had Aaron and Miriam and then all the children of Israel. Elijah led to Elisha. John the Baptist proclaimed the coming of Christ, who called His disciples—us.
In other words, we have a part to play as well. It is not the leading role but a supporting one. Nonetheless, it is a necessary part. There is no call for a "big head" here: God could have called someone else or raised up stones, as John the Baptist says in Matthew 3:9. However, He did not; He called us specifically (John 6:44). Therefore, we should not waste our opportunity.