The Boss is an immigrant political leader, and the true brains behind all city government, in the The Great McGinty. He first encounters Dan McGinty during the campaign for Mayor Tillinghast. He is impressed by McGinty's initiative and tolerantly amused by his brashness. In the course of their long association, however, the pair frequently come to blows, engaging in brawls, but tempered by mutual respect and even affection, as much as the tqo rogues are capable of anyway.
After the election, the Boss hires McGinty, since like him, he has guts with the "bare mitts." While in the limo, he talks about his past, the fact that he moved to America from a very poor country, where everyone lives "by chiseling everyone else." He imagines that in the old days, he'd have been a robber baron in a castle.
He gives McGinty money to buy a new suit (a "horseblanket" as he calls it), and assigns him to debt collection, strong-arming those who don't want to pay the Boss' protection racket. As with the Politician, the Boss defends his tactics, noting that if it weren't for him, *everyone* would be after his clients: "They'd be at their mercy."
Under the Boss' tutleage, McGinty rises to alderman, charging businessmen like bus magnate Mr. Maxwell a fortune for the city franchise. When Tillinghast comes under fire, the Boss suggests McGinty as reform mayor; naturally, the Boss is involved with the reform party, as he's *all* the parties: "You think I'm going to starve every time they change administrations?"
As part of McGinty's campaign, however, the Boss insists that he get married, now that women have the vote. Reluctantly at first, McGinty weds his secretary Catherine. The Boss later regrets this arrangement, as Catherine encourages her husband to do something honest once he's strong enough.
McGinty is elected to the governor's seat, and the Boss is proud and eagerly anticipating a fortune in such projects as building a new dam, since a dam is something you pour a lot of concrete (and money) into. McGinty confronts his mentor; when the Boss insults his wife ("Haven't you ever heard of Samson and Delilah? Sodom and Gomorrah?"), McGinty slugs him, and the Boss responds with a gun. He's quickly arrested, but soon after, McGinty is also exposed. Through help from the Politician, the pair, and the rest of their coterie, flee to South America. In the epilogue, the Boss is revealed as the bar owner, who once again brawls with McGinty when he catches him sneaking change from the till.
The Boss returned, along with McGinty, in the frame scenes for The Miracle of Morgan's Creek. McGinty is still governor, and when the Boss hears of the excitement in Morgan's Creek, his instinctive response is that "a little river needs a big dam!"