Why are these moral issues called “wedge issues”? A wedge issue is a smaller issue that almost everyone can agree on, used to increase support for the larger issue that people are divided on.
Something else to note about “wedge” issues. Abortion, racial preferences, the driving of faith out of the public square and gay marriage—the 4 most contentious “wedge”issues— all share one thing in common:
Democrats have advanced them by doing end runs around the democratic process. All have been decided entirely or in large part by judges. That makes them constitutional issues. People could lose on any of them in congress or in the state legislatures and not become inflamed by the result. There is always the next election. But when judges issue diktats which cannot be overriden by a vote...all hell breaks loose. Democrats have no one to blame but themselves for these “wedge” issues being so incendiary.
A “wedge issue” is one that splits a political base. It’s exploited by the opposition.
For example, blacks oppose gay marriage more than other democrats. If a politician were able to target blacks highlighting the Dem support for it, that would be using a “wedge issue.”
In politics, a wedge issue is something you use against your opponent and try to keep them from using against you.