Connor Lamb shocked the political world last week when he won a special Congressional election in a Pennsylvania district that President Trump carried by 20 points.

He might have also defeated a sense of invincibility for Republicans in two Central Ohio districts.

In the wake of Lamb’s surprise victory, the University of Virginia’s Center for Politics shifted its rating of Ohio’s 12th Congressional district from “likely Republican” to “leaning Republican.” That district was long held by Pat Tiberi, who stepped down last year to work at the private Ohio Business Roundtable.

Kyle Kondik, director of communications for the Center for Politics, says they’re also changed Ohio’s 15th Congressional district from “safe Republican” to “likely Republican.” The 15th district is represented by Rep. Steve Stivers, a military veteran and former Ohio state senator who’s held the seat since 2011.

The 12th district is the most interesting, Kondik says, because it’s part of Republican bedrock country. Before it was held by Tiberi, a Washington power broker, it was the seat of now-Gov. John Kasich.

“If in fact a Democrat wins that district in an upset, it may be because turnout is really good in the Franklin County parts of the district, and other parts of the district that might be more open to voting Democratic," Kondik says. "Like the Columbus exurbs in the southern part of Delaware County.”

Kondik says what’s happening in Ohio’s 12th and 15th districts is playing out in many districts around the country: More moderate Republicans are growing weary of the Trump administration and their party’s push to the right.

“Central Ohio is filled with a lot of traditionally Republicans voters who just aren’t necessarily fans of Donald Trump the way they might have been of, say, George W. Bush, or even more recently Mitt Romney,” Kondik says.

While Trump performed much better in Ohio than Romney, Trump’s margins were closed here than in many other parts of the state. That’s especially true in the 12th district. Hillary Clinton won Franklin County in 2016, and Trump’s margin of victory in Delaware County was smaller than his margin in many other Central Ohio counties.

Another reason the 12th district is so interesting, Kondik says, is that it’s currently empty. Following Tiberi's exit, 19 candidates stepped up to compete in the May primaries.

The leading Democratic candidates include former Franklin County Sheriff Zach Scott and Franklin County Recorder Danny O’Connor. On the Republican side, the best-known candidates include Ohio state Sens. Kevin Bacon and Troy Balderson, and Delaware County Prosecutor Carol O’Brien.

The primaries will obviously go a long way toward determining any upset potential in the August special election, which Kondik says will be the nation’s biggest special election since Lamb’s win in Pennsylvania.

The winner of the August election will fill out the remainder of Tiberi’s term. They’ll also have to win in the general election in November if they want to keep their seat when the new Congress assembles in 2019.