And it could have a snowball effect as well. As the number of border jumpers is reduced, it will be easier to detain them instead of playing catch-and-release. That in turn will make for even more of a deterrent, which in turn will reduce the number even further. Then we can concentrate more on internal enforcement (deportations, etc.), which would provide even more of a deterrent.
Just think of what effect it would have on someone living in Mexico if his friends and kin constantly keep returning home after being rebuffed in the attempt to get in the U.S., complete with tales of how arduous the trip was, and ultimately all for nothing. The psychological effect would be considerable.
And so would the monetary effect as many illegals pay "coyotes" to lead them across. Get sent back after you've already spent your life savings to give to a coyote and you're not going to try it again.