SHELBYVILLE, Ky. (AP) — President Donald Trump’s choice to challenge maverick Republican Rep. Thomas Massie of Kentucky announced his candidacy Tuesday, pledging to steadfastly support the president’s agenda while describing the incumbent as an obstructionist.

Retired Navy SEAL officer Ed Gallrein entered the 4th District campaign after gaining Trump’s endorsement. He will have the president’s vaunted political operation on his side, and a super PAC launched by Trump aides has already run ads attacking Massie. However, he will confront an entrenched, well-funded incumbent in Massie, who has consistently beaten back challengers, even when he incurred Trump’s wrath.

“I’ve dedicated my life to serving my country, and I’m ready to answer the call again,” Gallrein said in a release. “This district is Trump country. The president doesn’t need obstacles in Congress — he needs backup. I’ll defeat Thomas Massie, stand shoulder to shoulder with President Trump, and deliver the ‘America First’ results Kentuckians voted for.”

The GOP primary election contest next May will test Trump’s hold over Republican politics. Gallrein, who has never held elective office, was defeated in a state Senate primary last year.

The president’s dominance was on display recently in Tennessee, where a Trump-endorsed candidate won a crowded GOP primary for an open congressional seat.

Massie has won reelection by large margins since entering Congress in 2012 and has ramped up fundraising in anticipation of a significant political challenge this time around.

His reputation for being a contrarian who often opposes GOP leadership peaked this year with Trump, particularly on budget and foreign policy matters. Massie is counting on the belief that voters in the district will support his independent approach despite Trump’s popularity.

“Fourth District voters appreciate having an independent, conservative voice who works for them, and I look forward to continuing my fight for transparency, constitutional rights, secure borders, a true America-first foreign policy, and fiscal responsibility,” Massie stated on Tuesday.

Massie called Gallrein “someone willing to be a rubber stamp for globalist billionaires, endless debt, foreign aid, and forever wars.”

Gallrein, 67, is a farmer and businessman with a distinguished military career behind him. Meanwhile, Massie has the backing of Kentucky Senator Rand Paul, who joined him on the campaign trail last month.

Gallrein, aiming to target these issues, framed Massie as obstructing Trump’s agenda. “Thomas Massie has become one of the biggest roadblocks to President Trump’s ‘America First’ agenda,” he claimed, highlighting the need for a congressman who aligns with Trump’s vision.

Massie has also been vocal about potential legislation requiring the release of files related to Jeffrey Epstein, arguing against Trump’s tax and spending policies that, in his view, undermine economic stability.

Several other candidates have also entered the race for the 4th District, which covers northern Kentucky, with the ultimate Republican nominee expected to be heavily favored in a district not represented by a Democrat for two decades.