You can pull that kind of stunt when you have, or are running for, the executive; but if you want to get your veto-proof supermajorities working towards one end in concert, everyone needs to have run on - and with - the same playbook. Otherwise, you’re spending so much time trying to placate the squishies in your own caucus to get them onto the team that you’ll lose time and initiative. As much of an SOB as Newt Gingrich is, he had the right idea on how to get a legislative chamber moving in the same direction.
The mandate keeps your own troops in line, because you know the Republican Noise Machine will do its best to pick them off one by one.