I think Ted Cruz can appeal outside the base because he is brilliant by any standard, is able to clearly articulate and explain core American conservative principles of liberty, free markets and Constitutional law, and can apply those ideals in a compelling way to his public analyses of how they can turn this country around.
Best of all, he seems honest and sticks to his guns (which I think is something Americans will admire after 7 years of Obama's lies and prevarications) and is not afraid to confront the propaganda of left wing Democrat candidates like Hillary and Elizabeth Warren.
Frankly, at this point, I'm having a hard time seeing what other potential Republican candidate that I could support.
That said, one of the keys for me is a candidate who focuses his fire on the left, as opposed to running ritual purity litmus tests on other Republicans. I want a candidate who is willing to lead a crusade on two or three of the big make-or-break issues, not one who is busy painting himself into a holier-than-thou corner to eke out a narrow factional win in a primary.