It's been proven over and over, Americans DO NOT like extremists.. They hate them all, left or right..
And right now, on issues like immigration, women's issues, compromise(lack of it) the Republicans, especially the TP are seen as extreme, very hard-line.. And also a problem for the GOP is it's not just the party that are seen as extreme, their quasi spokespeople/conservative talking heads are seen as extreme too.. And the GOP refuses to distance themselves from those conservative talking heads.
Romney was on Hannity's show a dozen times or so during his run for the WH.. That's not the way to draw in younger and women voters..