I completely didn't get why you needed to trade - now I do. Apparently Unova Route 6 is the first place in all of the games (with exception to the Pal Pad) to catch Politoed in the wild, but you're not referring to that game (no way, they're native to UNOVA? Riolu definitely are, they moved in the two years between the games from Challenger's Cave to Sangi Ranch); you're referring to any other game in the series where it's NOT in the wild. I thought you just gave it a King's Rock and gained a level, but now I understand you actually have to trade it to evolve it. A pity. The anime didn't show the trading part, as I happened to see the evolution of Politoed using Ash's King's Rock.