Campaign hands cited the sharp profile Paul has cut in the Senate; his fluency on issues like privacy and Obama administration accountability, which are buzzy among young conservatives and libertarians; and his ability to get supporters to open their checkbooks.

“Rand Paul has a lot of grassroots energy he’s tapping into, the youth and kind of libertarian movement that other candidates just really haven’t grabbed a hold of yet, so that makes him kind of a unique, different choice that could inject some energy into the campaign,” said a source in one New Hampshire House race…

Paul’s appeal as a headliner isn’t limited to one region of the country — he’s well-regarded in the Midwest, said one aide there who picked him — nor solely to anti-establishment insurgents like himself.

A source in one incumbent’s campaign quickly fired off an email identifying Paul as their top pick: “Without a doubt,” the source said.