After the Trump-backed candidate in Texas’ 6th Congressional district runoff election lost this week, the pressure is now on the former President to prove his endorsement — one of his most powerful tools within the Republican Party — still holds significant sway in GOP primaries.

Trump endorsed coal lobbyist Mike Carey in the special election for Ohio’s 15th Congressional District in early June, throwing his weight behind a political novice in a race against a host of other Republicans, including multiple local elected officials. The Republican primary to replace former Rep. Steve Stivers, who left Congress earlier this year to lead the Ohio Chamber of Commerce, is Tuesday.

It’s a crowded race, with close to a dozen Republicans still vying for the congressional seat. This has led multiple Republican operatives, both in Ohio and nationally, to speculate that it is eminently possible for Trump’s candidate to lose the primary — and to acknowledge that yet another loss for Trump would dent his standing as a Republican kingmaker. It also could be personally frustrating for Trump, a politician who routinely bragged as President about the strong win percentage of the Republicans he backed in primaries.