Wouldn't the obvious answer to be vote against? If you do not know the terms of the deal, maintaining the status quo seems superior.

My understanding: You are one legislator among many; you have almost no power on your own. To deliver results for your constituents or to accomplish anything depends especially on party leadership and on other members of your party prioritizing your wishes over many other things. If you don't follow leadership, if you aren't on the team, they won't do anything for you.