Rep. Lou Barletta, R-Pa., found himself in a familar place this week: in President Trump's corner.

After the president's first speech to Congress earlier this year, he called out to Barletta. "There he is," Trump said. "My original supporter. You used to be lonely out there."

Now Barletta is ready to give Trump reinforcements in the Senate, which has at times seemed like lonely territory for the president. With Trump's support and encouragement, Barletta announced Tuesday that he will take on Sen. Bob Casey, D-Pa.

For Barletta, this means giving up a safe Republican seat in the House to try to replicate what Trump did last November: winning statewide in Pennsylvania against a favored Democrat, running in part as a strong voice against illegal immigration.

"I was probably one of just a few people ... in Pennsylvania who have any kind of chance in unseating Bob Casey, and I didn't go to Washington to protect a safe seat," Barletta told the Washington Examiner in a phone interview Wednesday. "I went to Washington to change it, and therefore I felt a responsibility to step up and risk my seat and take that challenge on."

Barletta appeared at numerous rallies for Trump after announcing his support in March 2016, frequently ginning up the crowd alongside Rep. Tom Marino, R-Pa., and becoming a top ally in Pennsylvania. He also served on Trump's transition team and was under consideration for transportation secretary.

Just as Trump has boosted Barletta, he could also doom his chances to defeat Casey, a two-term Democrat with a renowned family name in the state. Since winning Pennsylvania last year, Trump's approval numbers have sunk, with a recent NBC/Marist poll showing that only 33 percent of Pennsylvanians approve of the president's performance after nearly eight months on the job. Pennsylvania Republicans admit that those numbers have to tick up for Barletta to have any chance.

"Trump's got to do better," said former Sen. Rick Santorum, who encouraged Barletta to jump into the race. "If Trump's sitting at 35 percent, [Barletta's] going to have a heck of a time winning this race. Let's be honest about that. If he's sitting at 42 percent, Lou could win ... Trump's got to start getting stuff done, and stop picking fights and start picking winners."

Barletta, who represents the sprawling 11th District, knows Casey will be tough to beat. The incumbent has $5.6 million in the bank, as compared with only $512,000 for Barletta as of the end of June. Casey previously held two other statewide offices and easily beat Santorum in 2006, another year when there was an unpopular Republican president.

Casey also holds a statewide name recognition dating back more than 40 years as his father, the popular Robert Casey Sr., served as the state's governor from 1987-95. In fact, Casey's 2018 Senate bid will be the 14th time either he or his father will have appeared on a statewide ballot in either the primary or general election, beginning with his father's first gubernatorial bid in 1966.

Republicans concede that is a problem for Barletta.

"He has no great identity or track record. He hasn't really established himself as any kind of real record of success," Santorum said. "But on the other side, he hasn't really done anything that ticks anyone off. He's very low key, he doesn't do much or say much, and that tends to make you a hard target in an election."

Republicans are trying to paint Casey as having moved on from being a centrist Democrat to placate the far-left faction of the party, all the while forgetting "where he came from." Democrats are unmoved by the attacks.

"Therein lies the beauty and the..insurmountable challenge for Republicans to beat Bob Casey, because he is beloved in the Democratic Party," said T.J. Rooney, a former chair of the Pennsylvania Democratic Party from 2003 to 2010. "Now there are always going to be detractors, and his detractors, if they exist, I think, would generally be far left of center, of even where a lot of Democrats are."

The Casey campaign did not respond to multiple inquiries from the Washington Examiner about a potential matchup with Barletta.

Barletta believes his staunch opposition to illegal immigration could be the key to beating Casey. He gained national attention when he was elected mayor traditionally Democratic Hazelton, Pa., on that platform. In 2007, the city passed an ordinance that made English its official language and denied business permits to those who were found hiring illegal immigrants.

Whether it is Barletta or some other Republican on the ballot, Democrats will be running against Trump. They don't plan on letting Barletta carve out his own identity.

"[Trump] not only in every sense is on the ballot by virtue of the fact that he's president, he will be on the ballot by virtue of the fact, if Barletta succeeds in winning his primary... there will be no ambiguity about tying Lou Barletta to Donald Trump. It's his political godfather," Rooney said. "Donald Trump will not only metaphorically be on the ballot, but he will, in a lot of respects, physically be on the ballot. His image and likeness will certainly be front and center."

One area where Trump is likely to help Barletta is in a Republican primary. At the moment, Barletta is part of a crowded field for the nomination, including two state representatives and Jeff Bartos, a real estate developer and Republican fundraiser. Bartos, however, drew the ire of county chairmen in the 11th district when he ran a hard-hitting ad against Barletta.

For his part, Barletta is aiming squarely at Casey, who may be the hardest to beat of the ten Democratic senators up for re-election next year in states Trump carried in 2016.

"I was lonely when I first introduced the ordinance back in Hazleton. You couldn't get a politician to come near me," Barletta said. "There was nobody, and especially when people begin to call you names and mischaracterizing what you're standing for, it's not easy to stand there and take that criticism knowing that what you're doing is the right thing, and not wavering and backing down."

"That's what I saw in Donald Trump when he announced his presidency," he added. "That same courage to stand up against criticism and speak for the American worker and the American people. I just believe there's a common bond in that that he's not afraid, and neither am I. That's why I'm taking on a giant in trying to unseat Bob Casey because I'm not afraid either."