WASHINGTON — President Trump's rally in Wilkes-Barre Thursday night was billed as a chance to spark U.S. Rep. Lou Barletta, one of the president's most vocal supporters and a candidate for U.S. Senate.

But over roughly 80 rambling minutes, Trump's own accomplishments, grudges, and political imperatives dominated an evening that thrilled a packed crowd, but may also fuel his opponents.

Here are four key points:

Focus on 2020: Some key Republicans are practically writing off Barletta's chances against Sen. Bob Casey, Pennsylvania's incumbent Democrat — but Trump has a personal affinity for the GOP contender, and his own reasons to keep coming back to the Keystone State.

Pennsylvania is critical to his reelection — Trump opened with a long riff recounting his upset win in the state 21 months ago, down to reenacting the newscasts — but his 2016 victory has sparked a surge in suburban activism that threatens his grip.

In a state Trump won by 1.2 percentage points, any slippage could be devastating. That helps explain why Trump was back in Luzerne County, which swung his way by about 30,000 votes after supporting Barack Obama in 2012, making it a pillar of his coalition.

Barletta is already known well in the county, where he has been a mayor and then congressman for nearly 20 years. He told Politico that he'd hoped for a rally in Western Pennsylvania, where he is less known. But the president needs the state's Northeast to stay on his side.

Even if the Senate race drops from the national radar, there's good reason to expect Trump back before too long.

Sleepin' Bob: Trump praised Barletta as a "dynamo" and "incredible" and brought him on stage for brief remarks.

The president, though, is most comfortable on the attack, and he pinned Casey with a nickname: "Sleepin' Bob." As we've seen from "Crooked Hillary," "Lil' Marco," and "Lyin' Ted," this go-to move has worked for a master of marketing. (Though he might be running short on material: Trump in May called another Democratic senator, Indiana's Joe Donnelly, "Sleeping Joe.")

The Casey name, of course is ingrained in Pennsylvania politics, especially in the Northeast, since the Caseys hail from Scranton and his father was governor. Trump pointedly tried to separate the two, saying this Casey obeys Democratic bosses: "Not the father. But the son, yes."

(Trump also turned to one of his other campaign staples: making things up. He said Casey "wants to abolish ICE," the agency that enforces immigration laws. In fact, last week Casey said he opposed the idea.)

Casey has faced similar attacks before. His GOP opponent in 2012 called him "Senator Zero." But few people are as good at branding as Trump — whether that comes to building up his own products, or tearing down his rivals.

Grievances: The president devoted much of his rally to complaining.

That's not new, but it was a reminder of the stark contrast to how previous presidents used the power and prestige of office.

Trump spent the vast majority of his rally berating perceived enemies, mostly the "fake, disgusting news," various Democrats, and, of course, CNN, using the most powerful platform on earth to rant about a cable channel.

Even when touting his accomplishments on the economy and Supreme Court and reliving his 2016 election win, Trump used his successes to fuel gripes that he doesn't get enough credit.

Before a nearly all-white crowd, he repeated his frequent attacks on an African American congresswoman and outspoken Trump critic, Maxine Waters, as "low IQ." He used Central American gang MS-13 as an emblem of undocumented immigration, though its members represent less than 1 percent of gang membership in America and a tiny fraction of undocumented immigrants. He began a riff deriding Sen. John McCain (R., Ariz.), who is battling terminal cancer, before seeming to think better of it and moving on, a rare show of restraint. (Throughout, the crowd played along, even booing at the mention of McCain.)

About the only forward-looking initiative Trump offered was a renewed promise to build the wall.

Most presidents seek to advance a positive vision of where they want to take the country. Trump, to be sure, says he is making America great again for working people who have been forgotten — and, in many ways, his grievances are their grievances. They resonate with supporters who feel they have been denigrated by the media, business leaders, or the political elite. With poor approval ratings, Trump needs to keep his core supporters engaged.

That tack may work politically. It has also made Trump the angriest president in recent memory.

Cuts both ways: The rally thrilled Trump supporters, who credit him with a surging economy. In places like Northeast and Southwest Pennsylvania, the president clearly retains enthusiastic support.

But his presence also rouses his critics. Minutes after the rally, Gov. Wolf's reelection campaign sent out a fund-raising email highlighting Trump's praise for Wolf's challenger, Scott Wagner.

Democrats believe they can turn the swing suburbs around Philadelphia deep blue this fall, thanks to a backlash against Trump led by women.

Like Barack Obama, this president is a powerful motivator for both parties.

Staff writer Chris Brennan contributed to this article.

President Trump appears at a campaign rally for U.S. Rep. Lou Barletta at the Mohegan Sun Arena in Wilkes-Barre August 2, 2018.
TOM GRALISH / Staff Photographer
President Trump appears at a campaign rally for U.S. Rep. Lou Barletta at the Mohegan Sun Arena in Wilkes-Barre August 2, 2018.