NEW YORK —  In the heart of East Harlem on Saturday, the stage is set for Democratic Rep. Charlie Rangel.

Salsa and reggaeton beats from huge speakers pulse through the air at the 116th Street Festival. Vendors hawk every kind of Latin food imaginable — fried plantains, platters of just-grilled meats and “authentic” piña coladas, blended fresh on the spot.

At the back of a big stage where musical acts entertain a happy crowd of thousands, a half-dozen volunteers stand in T-shirts bearing huge photos of Rangel’s smiling face. A campaign worker staples a “RANGEL PARA EL CONGRESO” sign to a utility pole. The Congressman is slated to make a speech from the stage soon.

State Sen. Adriano Espaillat, Rangel’s main primary opponent, has just given short campaign remarks in Spanish, asking the cheering people for their votes, and he is now working his way through the crowd, shaking hands.

Espaillat’s volunteers, who number about a dozen, hand out campaign literature to passers-by and march alongside him holding huge placards bearing his face. Espaillat, a 57-year-old Dominican-American, is full of energy and a palpable ambition.

Time passes. The Rangel volunteers tepidly hand out some literature of their own, with a photo of Rangel standing next to President Barack Obama and the sentence “I HAVE A PROVEN RECORD!” in bold letters.

Eventually word begins to spread that the Congressman won’t be coming after all. The volunteers in Rangel T-shirts walk off.

The show goes on.

“That was because of a personal issue, not health,” Rangel says the next day. “I’m not explaining.”

He doesn’t need to.

If Rangel loses his bid for a 22nd term in the June 26 Democratic primary — and he may well — it won’t be because he didn’t show up at this event, the day before the famed Puerto Rican Day Parade. It won’t be because he didn’t have any public campaign events on a Saturday two weeks before the election.

Despite his age — Rangel turned 82 on Monday — the veteran lawmaker remains as fiery, as passionate and as likable as ever. And he retains a strong base of support among those who know him best.

But Rangel, in what is almost certainly his last bid for public office, is facing an unusually potent alignment of forces that make this the most difficult race of his career since he unseated longtime Rep. Adam Clayton Powell Jr. (D) in 1970.

Summertime Blues

Perhaps the force that rankles Rangel the most is the inevitable low turnout of a late June primary. New York has historically held its primaries in September, but a judge recently insisted on moving Congressional ones to June.

It’s problematic, Rangel acknowledges, and so are the abysmal approval ratings of Congress.

“They love voting for the president of the United States. They love voting for the governor. State legislators are closer to home,” Rangel says. “But the Congress [gets blamed for] every damn thing wrong in the world.”

He adds: “You add onto that that it’s not in November, dammit; it’s not in September, dammit; it’s in June, dammit — and we just told them last month! That’s a rough one.”

Another one of the forces that makes this a challenging race: The Campaign for Primary Accountability, a Texas-based anti-incumbent super PAC, has its sights set on Rangel.

His district has also changed. It now includes a chunk of the Bronx, a borough that Rangel has never represented.

When he was first elected, just under three-quarters of his district’s residents were black. After this year’s redistricting, Rangel’s newly configured district will only be about one-third black. It’s now a majority-Hispanic district, including big populations of Dominicans and Puerto Ricans.

Rangel, whose father was Puerto Rican, moves easily among an almost completely Latino crowd, dotted with notable New York politicos, at a Puerto Rican Day Parade breakfast in a Times Square hotel ballroom Sunday. People greet him like an old friend. “Hey, Charlie,” one smiling woman says.

Recovering from a back injury that kept him away from the Capitol for a long stretch earlier this year, Rangel carries a silver cane, but he uses it more to gesticulate than help him walk.

On the dais, he is greeted warmly by Rep. José Serrano (D-N.Y.), who has endorsed him. A few moments later, Christine Quinn, the Speaker of the New York City Council, gives a short speech to the crowd.

“Make sure we go out and … re-elect Charlie Rangel!” she yells.

Espaillat is at the event as well but gets the last speaking spot, when there are only about dozen people left sitting in the ballroom.

Bronx Is Up

In New York, the state of the Cuomos, the Clintons and Sen. Charles Schumer (D), political superlatives ought to be thrown around carefully. Still, Espaillat is easily the most ambitious challenger Rangel has faced.

“His level of ambition and aggressiveness is something to behold,” says an aide to one New York Democratic Member. “And I say that within the context of some very ambitious Manhattan politicians.”

Espaillat gets up early and goes to bed late. On Friday, coming back from Washington, D.C., he didn’t get home until 1 a.m., but he is out campaigning under an outdoor Bronx subway stop six and half hours later.

He flips from Spanish to English, depending on the commuter.

“Buenos dias, señor,” he says, greeting a voter going from the neighborhood to the subway. “How are you today? Good to see you. Come out and vote, alright? Á votar veintiséis.”

With metronome-like precision, he repeats the key point that he wants potential voters to take away from their very short interaction with him: Vote on June 26.

Most crack a smile, take his literature, shake his hand and then skim it as they walk up the steps to the subway platform.

Espaillat, whose state Senate district is mostly in the reconfigured 13th Congressional district, explains why he has been spending a lot of time in the Bronx.

“What I get in Northern Manhattan, he gets in Harlem, so, like, it balances itself out. This should be a decisive neighborhood,” he says, as a 4 train clacks overhead toward Manhattan.

Espaillat’s literature promises a Congressman who has “bold, new ideas,” but what differentiates him from Rangel, besides his relative youth, isn’t exactly clear.

“His influence has been dramatically diluted after his issues,” Espaillat explains, declining to specify what those issues are.

Rangel was censured in December 2010 for ethical violations.

Rangel allies argue that he still retains immense influence that a new Congressman just couldn’t match.

“A fresh, wet-behind-the-ears Congressperson will have the best intentions but will not be able to accomplish in their initial 10 years, what this Congressman can accomplish in six months,” Peggy Morales, a Democratic district leader, later tells Roll Call.

An Espaillat aide is handing out literature a few feet in front of the state Senator, so some commuters have already had a chance to peruse it by the time they get to the candidate.

“You look better in person,” a young woman tells him, holding his flier.

“I need your vote, OK?” Espaillat replies, undeterred from his message even by a compliment.

Many top New York politicians have compliments of their own for Rangel and his strong establishment support is part of why New York City insiders still think he’ll win his primary, if barely. But the once-vaunted Harlem political machine isn’t what it used to be. And it doesn’t stretch to the Bronx, where Espaillat is focused on running up a high vote total. In a low-turnout election, with four other candidates on the ballot, it might be enough to squeak out a victory. Or it at least sets him up to be the frontrunner when Rangel retires.

But for now, Rangel finds it important to explain why he’s still running. He asks and then answers his own question: “What the hell are you trying to prove? Haven’t you done enough in 80 years?”

“The answer is: If I can support the initiatives that we started, how can I possibly sit on the sidelines?” he says. “How could I spend the next two years, looking and wondering, what could I do? For all the efforts I spent my life, I can’t do it.”

Rangel gets into the passenger seat of his Cadillac, gives a salute and a wide-mouthed grin and then is off to the 54th annual Puerto Rican Day Parade.

He’s never missed one.