The age and party affiliation table from the latest Pew survey shows the demographics of party identification in great detail.  Pay attention especially to the marriage gap in the very bottom of that table: among 18-29 year olds, where the greatest gap between the two parties is to be found (58-33 D/R overall), there is essentially no gap among married people (44-43), but among the unmarried it remains a vast 30-point difference that benefits the Democrats (61-31).  As the overall number suggests, there are far more unmarried than married 18-29 year olds and significantly more than there have been in previous generations.  This is consistent with what others have been finding, and helps confirm one of the basic structural reasons why the GOP continues to have as much support as it still does and why its future in its current form is extremely bleak.