Imagine someone writing nearly 200 years ago: Dear conservatives, it's time to drop the slavery issue. No. We're not gonna give up. Full stop.
If the unborn is a human being (and embryology textbooks say that they are), then no matter how frustrating our votes seem to be wasted at times we still will never cease to try and defend life. The better way to go about it is to seek to educate people on the subject rather than use politics as our savior regarding the matter.