Paul has been critical of the Patriot Act (he's suggested parts of it are unconstitutional) and has said he would have voted against the Iraq War. Those stances make praising Paul hard enough for some mainstream Republicans, and we haven't even gotten to his view that drug legalization is an argument "best left up to the states" (he told Time he'd support federal drug laws however.)
Republican leaders are going to have a hard time integrating those views into endorsement speeches. (Thank goodness there's President Obama to rail against or they might really find themselves in trouble.)
And should Paul win in November, they'll have to deal with a Senator who libertarian Republicans consider one of their own Rand has said repeatedly that he's not Ron Paul, but his father's supporters are excitedly following and supporting his campaign anyway.
Then there are the tea parties. Where many in the mainstream GOP have acknowledged the tea party movement and even praised it for its tenacity, few have gone as far as Paul when it comes to reaching out to the group.
"The larger the victory the more the mandate for the tea party," Paul told the AP over the weekend when asked what a primary win would mean.
Tea partiers in Kentucky agree, according to one organizer. They're looking forward to getting a little respect from mainstream Republicans like Senate Minority Leader Mitch McConnell if and when Paul wins. Tea partiers see Paul as their ticket into the GOP tent, and they expect him to bring their values with him as he joins the establishment as Republican nominee.
"Mainstream Republicans try to steer clear of us," Louisville, KY Tea Party founder Wendy Caswell told me today. "A Rand Paul victory would mean that he [McConnell] has to pay us a little more attention."