proponent

Etymology

From Latin prōpōnēns, present participle of prōpōnō (“to put forward; propose”).

noun

1. One who supports something; an advocate.
   Proponents of the race — notably Mayor Michael R. Bloomberg and Mary Wittenberg, director of the marathon — said the event would provide a needed morale boost, as well as an economic one. November 2 2012, Ken Belson, New York Times, retrieved 2012-11-02
2. One who makes a proposal or proposition.
3. (law) One who propounds a will for probate.

adj

1. Making proposals; proposing.