I propose market regarding whether Senator Sanders and Senator Warren will both be candidates for President in 2020. This could either be a strictly YES/NO market regarding this specific question OR it could be made into a more specified market with the following brackets attached to this specific question. My suggestions are as follows:
Yes Both Sanders and Elizabeth Warren will be candidates for President in 2020
No Only Sanders will be a candidate for President in 2020
No Only Warren will be a candidate for President in 2020
No Neither Sanders or Warren will be candidates for President in 2020
I like the bet, because the two named senators are the leaders of the economic populist wing of the Democratic party. If only one of them would run, the wing would be united and increase the chances to succeed to make one of their own to president. That would influence other bet markets on PI.