Alan Brinkley, the Allan Nevins professor of history at Columbia University, is the author of "Voices of Protest: Huey Long, Father Coughlin and the Great Depression" and "The End of Reform: New Deal Liberalism in Recession and War." His most recent book is "The Publisher: Henry Luce and His American Century."

In the aftermath of the assassination of John F. Kennedy, the Washington Post began a series of editorials calling for an end to unregulated guns. Those editorials continued every day for months.  After a while, the editor gave up, and gun control eventually was forgotten – as it has been over and over again.

Now, almost five months after the killing of 20 first-graders in Newtown, Connecticut, riveted the nation, Senator Joe Manchin (D-W.Va.) is talking about trying to resurrect his bill on gun background checks that was defeated in the Senate last month.

Why is it so difficult to regulate guns in America?  Part of it is a result of the Second Amendment of the Constitution, which says “A well regulated Militia, being necessary to the security of the state, the right of the people to keep and bear Arms, shall not be infringed.”

Many Americans now believe that the Second Amendment means only using arms for regulated militias. But many people outside of big cities believe that keeping unregulated guns is part of what America means....