I saw a Massachusetts pickup with a "Scott Brown/He's For Us" bumper sticker, so presumably that was a previous slogan of his, not a current offering in his NH race. I have disliked that attitude when used by Democrats, and I find I don't like it any better when used by Republicans.
There is a superficial deniability that says "You know, us. He's for the little guy, the common man, the regular people, not the special interests/corporate bigwigs/career politicians/elites." Even if that is the conscious meaning, and sincerely felt, I don't believe it is the most powerful one. It is a tribal appeal, us against them, which is unhealthy. Plus, even if many people don't know that this is what is swaying them, there are those who know full well, and embrace it anyway.
We stand or fall together.