In recent elections, the Republican Party has gotten large majorities of the votes of white voters and of married voters. Unfortunately for the GOP, both groups are declining in size.
The Democrats have gotten large majorities of nonwhite voters and of singles. Both of these groups are growing in size.
In politics, demographics is destiny. To continue to be viable, Republicans need to find ways to become relevant to groups which are growing.
See an Associated Press article from the Tampa Tribune which wrestles with this issue. What nobody is saying is that our society teaches women to be more concerned with social issues than are men.