Why would a social conservative vote for Donald Trump, who is the least socially conservative of all the Republican candidates? I can think of a few reasons:

1. The big issues for social conservatives are abortion, gay marriage, and religious liberty (religious liberty being threatened as a consequence of gay marriage and civil rights laws).

2. On abortion, unless the Supreme Court were to revisit Roe v. Wade — something nobody foresees happening — the right to legal abortion is here to stay. Even if the Court overturned Roe, all that would mean is that the right to regulate abortion would return to the states. Most states would unhesitatingly protect abortion rights. Some would impose restrictions. In no state would it likely be banned outright. The possibility of there being an end to abortion achieved through judicial and legislative means is remote. That does not mean that having a pro-life president is unimportant, but it does mean that its importance has to be judged relative to other factors.