Whether conservatives should support federal legislation regarding abortion certainly involves difficult policy and political issues, but I want to flag as well that it also raises the constitutional one regarding Congress’s authority vel non to enact this or that statute. That is, even if one thinks it would be desirable as a policy and political matter for Congress to pass a particular bill, conservatives ought not to support it if Congress lacks the constitutional authority to do so.
There are a wide variety of possible statutes that Congress might enact in this area, and there are also a variety of possible fonts of constitutional authority that Congress might invoke. Results may vary: Congress using its spending authority to say that federal funds may not be spent on abortions is one thing, invoking the Commerce Clause to ban all abortions is another. Needless to say, conservatives should honor constitutional limits, and they should be especially wary of stretching federal powers to advance their agenda when the precedent thereby set will be used by the Left to stretch powers in exactly the same way to advance its agenda: Remember our disappointment in the Supreme Court’s decision upholding the constitutionality of Obamacare; think how a Democratic president and Congress would love the authority to define the meaning of every clause in the 14th Amendment; consider also the precedent that might be set regarding the relative authority more broadly of Congress vis-a-vis the states.
I’m no expert on all the possible statutes that might be enacted, nor regarding all the constitutional issues raised. Just saying be careful.