The Jacket Party Manifesto
You might expect Japan to be all politicked out after the last couple of months of campaigning, voting, and editorializing for the New York Times and Mu. But you would be wrong. Just today I noticed that a new party had leapt into the fray with the publication of its "Jacket Party Manifesto" (ジャケット党宣言) in the current issue of underground anarchist review Non-no.

The Jacket Party itself seems to consist of a number of factions, including a right-wing splinter group of militaristic yet feminine biker types, but they claim broad popular support: "This autumn, everyone will [rally behind] the Jacket Party Manifesto!" Their specific campaign promises include increases in fashionability of 100% or more.
But seriously, using 党 (-tō, "faction, party") to specify taste cliques ad hoc is a common technique in Japanese. Two of the oldest and best-known non-political parties here are the amatō 甘党 and karatō 辛党, the Sweets and Spicies respectively. Today these are often used to mean "People with a sweet tooth" and "People who prefer spicy food" respectively, but the original opposition was between sweets and booze.
Another group that welcomes drunks is the satō 左党, "Left Party," so named because "left-handed" (hidarigiki [or, more commonly, hidarikiki]) is also slang for a hard drinker. The most commonly given etymology for this, found in sources like UMEGAKI Minoru 楳垣実's Ingo jiten 隠語辞典 ("Dictionary of cant"), makes it an Edo pun: workmen would hold their hammer in their right hand and their chisel (nomi 鑿) in their left, making the left hand the nomi hand, and equally so when the nomi in question is the other one, meaning "drinking" (飲み). This seems rather fanciful as etymologies go, but elaborate wordplay was the cornerstone of Edo culture.
The more prosaic alternative explanation is that you drink with your left hand so that your right hand can more easily hold the bottle to pour from and/or grab your sword when things get drastic. It's also worth noting that most books of etiquette recommend that men hold the sake cup in their left hand even today.
Charles:
How odd, now that I think about it, I drink left-handed. I always thought this was because you wanted to keep your right hand dry so you could light matches, smoke, or do other things requiring a nonslip grip.