It's not often they turn up the volume on the televisions at McGillin's Old Ale House, the city's oldest tavern.

"Eagles games, national championships - and this," said owner Chris Mullins. "This is important. This is blood sport."

With the presidency on the line.

Across the region, sports bars, dives, and other establishments opened their doors and welcomed the partisans Monday night for the first debate between former Secretary of State Hillary Clinton and real estate mogul Donald Trump.

Like so many historic, if not record-setting, television events, it meant an opportunity to gather with friends or coworkers, like-minded or not. As the nominees met on a stage on Long Island, viewers settled in at parties in the Piazza in Northern Liberties, in Kensington, in Warminster. The city's Republican Party gathered to watch from its headquarters in Mayfair.

At McGillin's, which opened the year Abraham Lincoln was inaugurated, patrons munched on Trump Tower meat loaf and Hillary hoagies, washing them down with blueberry lemonade vodka or red ale. Campaign signs and oversize candidate photos hung from the walls, and customers received handout fans plastered with their preferred nominee's face.

"We are Philadelphians and we do boo Santa Claus - but let's all be civil tonight," Mullins told the split crowd.

And while Philadelphia may be a Democratic stronghold, his bar leaned red Monday, thanks in part to Trump-leaning out-of-towners here for a cable TV engineers conference.

Shane Broyles pumped his fists when Trump knocked Clinton for 30 years in politics.

"This is fun. He's got her over the rails," said Broyles, in town from Kansas for the conference. "He's killing her tonight."

Next to him, Detroit lawyer Ray Foley turned away to face another TV.

"I think [Trump's] winning the debate but it's because he's yelling a lot, he doesn't follow decorum," said Foley, a Clinton supporter. "She needs to stop trying to explain things he says and just ignore him."

His wife had a different take. "As a reluctant Hillary voter, she's making me feel better," Brittany Foley said, "convincing me I'm voting for her and not against Trump."

A few tables away, Joost Remmers and Thijmen Jaspers Focks, 22-year-old civil engineering students from the Netherlands, were incredulous over Trump's rise and success as the GOP nominee.

In the Netherlands, Remmers said, Clinton would be considered very conservative. What does that make Trump? "Just an idiot," Remmers said. "In my country, Clinton would win by 95 percent."

Mullins, the tavern owner, is for Clinton. His bar stayed afloat in its early years, he said, when another "strong woman" - "Ma" McGillin - sold "tea" from a side door during Prohibition.

Blocks away, at American Pub, at 15th and Market, a watch party hosted by the government watchdog group Committee of Seventy was younger, more local, and almost exclusively pro-Clinton. The standing-room-only crowd there erupted in cheers when Clinton told Trump the reason she hadn't been campaigning as he had been in recent days because she was preparing for the debate, like she's been preparing to be president.

It won't be their only chance to cheer. Two more presidential debates loom - Oct. 9 in St. Louis and Oct. 19 in Las Vegas.

Dennis Bora, 30, of Center City, thought Clinton was clearly more poised and prepared. "Trump couldn't finish sentences. I thought he was worse tonight than in the Republican debates," Bora said.

Back at McGillin's, Foley, the Detroit lawyer, said he thinks Clinton will ultimately win the presidency - even if he doesn't think she won the first debate.

"Most people here have made up their mind. I think they're just here to watch a show," he said. "And it is a show."

jterruso@phillynews.com

215-854-5506   @juliaterruso