Rep. Mike Pompeo (R-Kan.) has a challenger. (AP Photo/Charles Dharapak, File)

Welcome to day two of what's already shaping up as one of the most heated U.S. House Republican primaries of 2014.

We're talking about the race in Kansas's 4th District, where former congressman Todd Tiahrt  announced Thursday that he would challenge Rep. Mike Pompeo. Things are already getting testy.

Tiahrt, who represented the district from 1995 until 2011, kicked off his campaign with a speech in which he sharply criticized Pompeo, arguing there are "big policy differences" between the two. Claiming that Pompeo had been too hawkish on Syria, too accepting of the government's sweeping surveillance efforts and too soft on Obamacare, Tiahrt made his case for why a change is necessary.

"I’m also opposed to Mr. Pompeo’s special interest legislation to block us consumers from getting information about our food and his efforts to prevent us from seeing complaints about defective products and so on," said Tiahrt.

In a statement responding to Tiahrt's entrance into the race, Pompeo accused his opponent of "politician doublespeak," noting that he was previously a supporter.

"I am surprised that Todd has chosen to attempt to get back the job he abandoned back in 2010," Pompeo said. "Todd endorsed me in my run for Congress that same year, my first effort to seek political office. Todd also endorsed me in my second campaign, my successful reelection to Congress in 2012."

Adding fuel to the fire, the antitax Club For Growth -- which isn't shy about spending big money in campaigns -- swiftly rallied to Pompeo's side with an endorsement. The group called Tiahrt's voting record "liberal."

And that was all just on Thursday.

The stakes are high, considering that the winner of the GOP primary will be expected to dance to victory in the general election. The 4th District is safe Republican territory and where Mitt Romney won 62 percent of the vote in 2012.