You might direct liberals & libertarians to Nat Hentoff...
http://groups.csail.mit.edu/mac/users/rauch/nvp/hentoff.html
He has some excellent arguments for the pro-life position.
Pro-life Republicans would have a better case if they used a human rights arguement. Abortion butchers physically weak and politically powerless living human beings in American society simply because these weak and powerless living human beings are an inconvenience to the permanent ruling aristocracy in Washington D.C. and their ministers of truth in America’s newsrooms and faculty lounges.
Pro-choice Republicans would offer irresponsible parents the choice of which doctor fixes them (vasectomy/tubectomy) when they become parents for the second time without the ability to provide basic needs for the child they produce.
Every federal judge and judicial nominee should be able to explain the difference between a living human being and a human being that isn’t alive. Same with U.S. Senators and Representatives.