That's how things work in DC.
1. The party in control writes a bill that most of their party will vote to approve.
2. Then they make deals with members of the party that lean more towards their side (overly liberal or overly conservative).
3. If that doesn't get them the votes they need then they make deals with members of the party that lean more towards the center.
4. As a last resort they make deals with the centralist from the other party.
Please note we very rarely make it to step 4.

Sadly there is a one step process that is almost never used any more:
1. Both parties work together to make a bill which will pass by the majority of both parties elimnating any/all deals & admendments.