Senate Republican Leader Mitch McConnell's reward for his deal with Democrats to lift the default threat: a burst of oxygen for his tea party primary challenger.
That would be Matt Bevin, a 46-year-old investment executive who has aligned himself with Sen. Ted Cruz's challenge to Obamacare. Bevin dismisses warnings from Wall Street and elsewhere about a default, as well as polls showing that the shutdown was a disaster for the Republican Party.
"There was no threat of default," Bevin said at his campaign headquarters outside Louisville, Ky. "Many of these things are Chicken Little-like, the sky is falling, when in fact that's not the case."
"I understand exactly what polls are telling us, but you have to look at the source of those," Bevin said. Referring to the hero's welcome Cruz recently received in Texas, he added, "I also see the very man who supposedly was responsible for this hurting just received an eight-minute standing ovation when he went home to his state."
Bevin faces an uphill fight to oust McConnell, who was first elected in 1984. But tea party challengers have knocked off other Republicans, such as former Sens. Robert Bennett of Utah and Richard Lugar of Indiana.
So McConnell, who has vowed to build the greatest U.S. Senate campaign ever, can't afford to ignore the threat. His allies have attacked his primary foe as "Bailout Bevin" for state aid a family company received after a fire and have accused him of paying taxes late.
Bevin shrugs off the attacks as untrue. He says he'll need $4 million to $8 million to win, even if McConnell pulls in $20 million more than that. Though he has seeded his campaign with some of his own wealth, he said he will raise most funds from donors.
Bevin has a symbolic tie to Wall Street—a family company made the bells that for years rang the New York Stock Exchange in and out of sessions. But like other tea partiers, he said the GOP has too often aligned itself with "larger corporate interests" at the expense of everyone else.
(Read more: Not everyone vowing to avoid another govt shutdown)
One issue he attacks McConnell is immigration, saying the Republican leader and parts of the business community have supported "amnesty" for those who entered the country illegally.
As President Barack Obama seeks to turn Washington's attention back to immigration, the attack shows that McConnell will continue to face home-state pressure from the right on more than just Obamacare and government spending.
—By CNBC's John Harwood. Follow him on Twitter: