"Rep. Lou Barletta, a Great Republican from Pennsylvania who was one of my very earliest supporters," President Donald Trump wrote on Twitter. | Evan Vucci/AP Photo Trump: Barletta 'will make a fantastic senator'

President Donald Trump on Sunday sought to bolster Pennsylvania Republican Rep. Lou Barletta's Senate campaign, as the early Trump supporter competes in a primary to face incumbent Democratic Sen. Bob Casey.

"Rep. Lou Barletta, a Great Republican from Pennsylvania who was one of my very earliest supporters, will make a FANTASTIC Senator," the president wrote on Twitter.


Trump pointed out that Casey opposed the passage of the GOP tax plan, an argument the White House is employing against Democratic senators who are up for reelection in states the president won in 2016. "Voted for Tax Cuts, unlike Bob Casey, who listened to Tax Hikers Pelosi and Schumer!" Trump tweeted about Barletta.

Barletta, a four-term congressman and former mayor of Hazleton, is among a handful of Republicans vying to challenge Casey in a state where the president narrowly edged out 2016 Democratic nominee Hillary Clinton. State Rep. Jim Christiana, another Republican seeking to challenge Casey, has received endorsements from the top lawmakers in the state House and Senate. But Barletta received the backing of the state Republican Party.

Barletta was among House conservatives who led the opposition to immigration reform during the Obama administration, after the Senate passed a sweeping and bipartisan compromise.

Trump praised the Pennsylvania congressman but did not endorse him during an October rally in Harrisburg, Pennsylvania, where he called Barletta a "great guy" and predicted that he would win "big."