Steve Voss, a political science professor at the University of Kentucky, says it isn't likely Bevin will be able to repeat Paul's 2010 primary insurgency.
"I don't think there's a difference between the electorate now and the electorate then – I think the difference is between Rand Paul and the other tea party candidates we've seen emerge," he says. "[Paul] had vast resources from outside the state once his candidacy started being taken seriously because of his father."
Voss says Bevin matters – but only insofar as he pulls McConnell to the right and jeopardizes his general election chances.
"How many concessions does [McConnell] have to make, how many promises to the right, in order to put this primary challenge away?" says Voss. "So most likely that's the threat – does McConnell have to alienate a lot of middle of the road voters in order to beat back this challenge?"
State Senate Majority Leader Damon Thayer, also a McConnell supporter says Bevin isn't even a blip on primary voters' radar.
"I don't see Matt Bevin influencing this race at all," he says. "The tea party does remain strong in Kentucky, but it's regional. Most Republicans here recognize we are in a position of strength and Mitch McConnell is our best chance to stop the Obama agenda."
But already Bevin's campaign has hit McConnell for so far declining an effort led by conservative Senate leaders Cruz, Mike Lee of Utah and Marco Rubio of Florida, to threaten a government shutdown unless President Barack Obama's signature health care law, the Affordable Care Act, is defunded.
And Bevin thinks as long as he campaigns hard and raises enough money – including spending his own – to compete, he's still a tea party candidate who matters.
"The people of Kentucky want a fiscally conservative and socially conservative senator and I am the best opportunity for them; it then becomes a function of allowing them to understand that," he says. "This will be won from the grassroots level, from the ground up."
Corrected on : Correction 8/8/13: This story has been updated to correct a transcription error – an extra ‘is’ originally appeared in a quote from Steve Voss.