I think the notion that any mainstream candidate would accept a debate with someone they didn’t need to is pretty ridiculous. (…Let alone for a measly few points…which aren’t even guaranteed…as the supporters of the person who dropped out could still vote for anyone or not at all.)
And how the hell do you determine the winner of a political debate?? You gonna…take a vote?
And besides, if the other candidate really was such a threat, the major opponents could easily just work the rules and the media environment to their favor and railroad him out of commission anyway. I’m pretty sure I’ve seen this somewhere before.
And perfect example is when Peter Schiff was running in for US Senate, he and his Primary opponents had one single debate, early in the campaign. He was constantly asking for more, ready to do so any time, any where. Neither of his opponents would agree to another one. After all, why should they? They had better name recognition, and he was a better speaker. They had everything to lose and pretty much nothing to gain. Plus, after the first debate one local paper said Schiff came in first, and nobody came in second…the other two opponents tied for third. Feel free to watch for yourself.
It sounds like you’re offering a very real chance to lose an election in exchange for a very slim chance to gain a few points (which have an even slimmer chance of affecting the outcome a lot of the time.) I just don’t see why any mainstream candidate would accept your deal.