[BroJoeK]

DiogenesLamp: "You would have us believe that they controlled the Congress, and had a total commitment to slavery, but for some reason didn't bother voting on a law to extend it to the territories?
Either they didn't have a "commitment" or they didn't have "control." "

But they did, it was the 1850 Compromise which, among other things, defeated the Wilmot Proviso which would have outlawed slavery in US territories.

Of course slavery was an emotional issue which could sometimes override partisan loyalties.
But more mundane Washington matters such as specific tariff rates, government spending allocations or navigation rules were more subject to regular order and the power of Southern committee chairmen, the finance committee for example.

[DiogenesLamp]

But they did, it was the 1850 Compromise which, among other things, defeated the Wilmot Proviso which would have outlawed slavery in US territories.

You are trying to dodge the point again. You allege the Southern states had a total commitment to slavery, and you also allege they controlled congress.

If both of the things you allege were true, there would be no need for "compromise" and there would be no possibility of such a thing as the "Wilmot Proviso" even making it to the floor.

Now you've been caught. You have to discard one claim or the other, because they are patently contradictory. Both cannot be true or the "Missouri Compromise" (which was itself unconstitutional) could not have made it through congress. The majority that is committed to something do not "compromise" regarding it.