"All of these things presented probably the best possible opportunity in a very long time to have significant legislation coming out of Congress, " said Kristin Goss, a professor at Duke University's Sanford School of Public Policy.

WSJ: Background-Check Gun Measure Fails in the Senate

"His engagement would send a very strong signal to people who are wavering" that supporting expanded background checks would be, "if not a safe vote, then not as dangerous a vote as the conventional wisdom might hold, " said Kristin Goss, a professor at Duke University's Sanford School of Public Policy.

WSJ: New GOP Voice in Gun Talks