HARRISBURG — Four-term U.S. Rep. Lou Barletta, a staunch supporter of President Trump who first got national notice as a small-city mayor for his attempted crackdown on illegal immigration, on Tuesday won the Republican nomination for U.S. Senate in Pennsylvania.

Barletta had paid little attention to his Republican rival, state Rep. Jim Christiana, during the primary campaign. Instead, he focused his attacks on the candidate he hopes to unseat in the fall, two-term Democratic Sen. Bob Casey.

Barletta is a favorite of Trump, whom Barletta endorsed in 2016. Trump asked Barletta to run for Senate, and the president is expected to visit Pennsylvania to campaign for him.

Congratulations to Lou Barletta of Pennsylvania. He will be a great Senator and will represent his people well – like they haven’t been represented in many years. Lou is a friend of mine and a special guy, he will very much help MAKE AMERICA GREAT AGAIN!

— Donald J. Trump (@realDonaldTrump) May 16, 2018

Casey, who was unopposed for the Democratic nomination, has opposed Trump’s Supreme Court pick, many of his highest-profile nominees and the GOP tax-cutting law.

Casey is among 10 Democratic senators seeking re-election this year in states won by Trump, making Casey a target for Republicans.

Trump edged Democrat Hillary Clinton by less than 1 percentage point in Pennsylvania in 2016’s presidential election. Republicans control the Senate, 51-49, and defeating Casey would give Republicans one more pro-Trump vote to help advance the president’s agenda.

Still, defeating Casey in November’s election is a tall order.

Casey, the son of a late former governor, has strong name recognition and has won five statewide elections, including two as auditor general and one as state treasurer. He also has a huge cash advantage, with about $10 million in the bank at the end of April, compared with Barletta’s $1.3 million.

Casey, 58, is popular with labor unions and backed former President Obama’s signature policies.

Barletta, 62, won his House seat during the Republican midterm wave of 2010, catapulted by the attention he received while mayor of Hazleton for attempting to use local laws to crack down on immigrants in the city who had entered the country illegally.

Barely any outside money has made its way into Pennsylvania to help Casey or Barletta, making it extremely unlikely that residents will see a repeat of the record-breaking $180 million U.S. Senate race in 2016 that Pennsylvania’s Republican Sen. Pat Toomey won by fewer than 2 percentage points.