BOWLING GREEN, KENTUCKY - Republicans in a number of U.S. states head to the polls in coming weeks to vote in primary elections to pick the party's candidate for November's midterm elections.  The primaries in some of these states are seen as a test of the conservative Tea Party movement, which has been influential in Republican party politics since scoring significant victories in the 2010 midterms.

In Kentucky, Senate Republican Minority leader Mitch McConnell faces a primary challenge from a Tea Party-backed candidate.   But, waning enthusiasm for some of the Tea Party candidates could affect the outcome of these races with party control of Congress next year hanging in the balance.

Conservative Kentucky businessman Matt Bevin has forged a well-traveled path throughout Kentucky in his bid for the U.S. Senate.  He says he hears the same concerns among voters across the state.

“They’re worried about the economy.  They are worried about their ability to maintain their own jobs, let alone their children and grandchildren," said Bevin.

Those are the concerns of Bowling Green, Kentucky voters such as Brian and Claudia Strow, who are looking for a candidate that can best bring job growth to Kentucky.

“Our unemployment rate is still much higher than the national average, it is 7.9 percent here in March.  People are looking around trying to ask what kind of government policies might be conducive to job creation," said Claudia Strow.

Bevin is popular among conservative Tea Party voters who were key to midterm election wins nationwide in 2010 that changed the balance of power in the U.S. House of Representatives.  

Their concerns:  what they see as government intrusion into their lives, especially President Obama's health care reform law.  

Republican Senate candidate in the Midwest state of Iowa, Matt Whitaker, says four years later, conservative voter outrage over President Obama's health care reform continues.  

Whitake: “It’s probably the number one issue on the minds of a lot of voters."
Reporter: "Why?"

Whitaker: "Just because.  It’s having a significant impact on people’s lives.”

But it might not be enough of an impact to draw out as many voters this midterm election cycle, says University of Kentucky Professor Al Cross.

“I think there is some fatigue among people who were all energized by the Tea Party," said Cross.

Such as in North Carolina, where the Republican establishment candidate recently defeated Tea Party rivals to win his party's Senate nomination.   

Yet it's a different story in Nebraska, where Tea Party backing helped Ben Sasse win the Republican Senate primary.  

But in Kentucky, despite Tea Party support, Matt Bevin trails incumbent Republican Senate Minority leader Mitch McConnell in polling, even though McConnell’s approval ratings are very low.

“McConnell, interestingly enough, had about the same job approval numbers as Obama, in one of the polls early in the race.  There’s just not a great reservoir of love for Mitch McConnell," said Cross.

If McConnell does win the primary, the race against his likely Democratic challenger in November's general election could be one of the toughest of McConnell’s career.

“It matters, because he is the leader of the Republicans, and he is the most vulnerable Republican incumbent by far," explained Cross.

It is a seat Cross says Republicans need to win in their national strategy to secure a majority in the U.S. Senate.  And this could hinge on whether Tea Party-backed candidates help or hinder Republicans in achieving this goal.