Republican groups are dropping hundreds of thousands of dollars into Arizona in the hopes of keeping any prospect of another Democratic upset in next month's special election at bay.

The GOP says it's confident that the party will keep control of the seat last held by ex-GOP Rep. Trent Franks, which represents a historically Republican area with a strong core of reliable GOP voters and retirees.

Still, national Republican groups have recently committed more than a half-million dollars to retain what should be a safe seat, which President Trump won by 21 points in 2016. 

The investment underscores how the uncertain political climate is forcing the GOP to spend on races that should be easy Republican wins, especially after a shocking Democratic upset in Pennsylvania's 18th District earlier this month.

"I'm skeptical the Democrats can actually win, [but] the more activity there is on the Republican side, the more indication it is actually competitive, because the parties are the ones with the best numbers," said Kyle Kondik, an elections analyst with the University of Virginia. "Losing Pennsylvania 18 was pretty embarrassing for Republicans. This would be worse."

The Arizona race pits former state Sen. Debbie Lesko (R) against Democrat Hiral Tipirneni, a physician and first-time candidate, in the April 24 election. Franks resigned from the seat in December after allegedly discussing paying a staffer to carry his child.