Why Is Trend on Abortion Regulation Counter to That of Gay Rights and Marijuana Use?

The Washington Post - The Fix blog: If gay marriage and pot are now OK, why isn’t abortion?, by Juliet Eilperin & Scott Clement:

As abortion opponents are scoring a string of victories in the states, it raises a question: why are conservatives gaining ground in this one arena, even if they’re losing in the battle over gay marriage and marijuana?

A few factors help explain this contradiction. . . .