I could see that being possible for President of Senate having a casting vote. Perhaps, argued by Federalists that this would be a good to help government run more smoothly. Though I could even see it being a deal-breaker to States adopting the Constitution, if the Federalists insisted.There's a massive issue why I feel it wouldn't: slavery. Even if you disregard the federalism concept that states would feel one state/ one person would be over repersented in the Senate if The President of Senate had a casting vote ,it would upset the balance of slave/ free states. Suppose there where eleven free states eleven slave states. There would be twenty-two senators for preventing/abolition slavery twenty-two for spreading/preserving slavery. It would be hard enough for a divided Senate find someone they can all find acceptable to preside, if the President of The Senate had a casting vote it would upset both Northern interests and Southern interests. I would argue if The President of Senate was given a casting vote at convention, I could see a President of Senate's casting vote being the cause of much constrversy even bringing the States to civil war.