WATCH: How Will Republicans Deal With Marriage Equality in 2016?

Marriage activist and author Marc Solomon predicts Republicans will soon have to abandon vitriolic messaging against marriage equality, if the party wants to recruit younger voters.

"I don't think we'll have a freedom to marry plank [in the Republican platform] but I think they will start getting rid of this language," Solomon told Meet The Press's Chuck Todd on Sunday while discussing his new book, Winning Marriage.

Marriage rights for same-sex couples have evolved from a decade ago, when voter referendums were used as a wedge issue at the ballot box, and support was seen as a weakness for left-wing politicians. Solomon's account, however, shows how the tide has turned.

"I don't think it'll be a setback," Solomon said. "I remember a time when it was used against us by the GOP and it was an issue in the Democratic primary as well. Now it's a driver for Democrats, and Republicans want to stay away from it."