You divide the damage as you cast Electrolyze, not as it resolves. Each target must be assigned at least 1 damage. In other words, as you cast Electrolyze, you choose whether to have it deal 2 damage to a single target, or deal 1 damage to each of two targets.
17-11-2017
wotc
If all chosen targets are illegal as Electrolyze tries to resolve, it won't resolve and none of its effects will happen. No damage will be dealt and you won't draw a card.
17-11-2017
wotc
If Electrolyze targets two creatures and one becomes an illegal target, the remaining target is dealt 1 damage, not 2. You'll still draw a card.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.
Zoltan Boros & Gabor Szikszai2015-05-22
