FDR essentially pioneered the modern use of the omnibus bill by threatening to veto any assistance to the poor/elderly that didn't include social security. Basically his goal was to make the poor starve if social security didn't pass, and blackmail politicians into being forced to vote for it.

Of course this was all predicated on the other prong, which was the 'switch in time that saved 9' where he also threatened to pack the courts to ensure it was found 'constitutional'. FDR was quite ruthless in his destruction of constitutional and democratic controls, and now so much of our government depends on it that it's effectively politically impossible to unwind.