There are many arguments about how long Polyamory has been alive. Some claim it has been around forever with beginnings in the animal kingdom. Others believe it was a child of the 60's that came into awareness in the 70's. And even others, I'm somewhat in this camp, believe it is still evolving. What they don't really disagree on is that the number of practicing Polyamorists is fairly low. Throw a rock in a crowd and you will likely hit a monogamous person. Throw 10 rocks in the same crowd and it is possible you will never hit a Polyamorist. Apply these odds to dating and a question or method is born; conversion.
I have known a few people who openly state they will try to convert monogamous people to polyamory. I've known a few more who will tell you they are open to dating monogamous people because "You just never know". I have even met a few who seem to think that converting anyone and everyone they can get their hands on to Polyamory is their lot in life.
I'm not convinced that conversion is the way to go. I've dated my share of monogamous people and even tried it myself for a time. When I was lucky the relationships ended quietly with both of us acknowledging the fact that we had incompatible lifestyles. When I wasn't lucky things blew up and love was replaced by bad feelings and even hatred.
Does it make sense to date a monogamous person in the hopes of converting them to Polyamory?
The downside, as I mentioned, is the relationship blowing up in your face. Assuming it blows up, if you are lucky it will happen soon. If you aren't lucky you may struggle for years before finally being forced to admit defeat. One or both of you may struggle with serious jealousy issues. Trying to solve those may result in the creation of rules designed to protect feelings and one or both of you may find the rules difficult or impossible to follow. Or you may try to take things as they come resulting in a pattern of highs and lows, giddy good times and turbulent bad times.
The upside is that you could end up with a perfectly wonderful relationship. Making a guess, by the time that happens you will have been through a lot with your new partner which would hopefully make for a fairly solid relationship.
Because I don't believe trying to convert people is a good way to go my approach is a bit different. I will date a monogamous person but with certain conditions. They must understand very clearly that I am polyamorous and that won't change. I am also very clear that if their monogamy begins to effect my other relationships that will be the end. And if I feel our relationship is hurting them morally or emotionally I will probably want to end the relationship. I also won't be a dirty secret for anyone. Spouses or other partners will need to know about and bless our relationship. If any of those things don't fit, aren't agreeable, or I don't get a sincere feeling from the other person about them I will not get involved with them. Often when I date a monogamous person I take the relationship at a very slow pace. If at any point things don't feel right I will stop and talk with them about what is happening to determine if we want to continue the relationship.
Where are you at with conversion? Good idea? Bad idea? Have you ever tried it or been the subject of a conversion?