I am working on a Magus and keep getting myself confused over the rules, where they concern attacks with touch spells.
When attacking with a touch spell using unarmed strike (how most spell casters make the attack), you make your attack roll of 1d20+str+bab against the touch AC. If successful then the spell takes effect, and if you miss you have a held touch spell. If you manage to beat their normal AC, do you also get to deal the damage as if you made a successful unarmed strike?
When attacking with a ranged touch spell, you make your attack roll of 1d20+dex+bab against the touch AC. If successful then spell takes effect, and if you miss then the spell is wasted, and it is not held unlike with touch spells.
When using spell strike to deliver the spell with a weapon, you make your attack of 1d20+str+bab, but which AC am I trying to beat? If I beat the touch AC but not normal AC does only the spell happen? If I beat the normal AC but not the touch does the weapon damage and not the spell? If I beat both AC's does both the weapon and spell take effect?
When making an attack with a spell that has a range of touch, a caster can either on the same turn as casting the spell (or on later turns as touch attack if still holding the charge) make a typical touch attack as described in Combat on Armor Class on Touch Attacks and in Magic on Range on Touch or on subsequent turns after casting the spell the caster can "make a normal unarmed attack (or an attack with a natural weapon) while holding a charge" (emphasis mine) as described in Combat on Cast a Spell on Touch Spells in Combat.
It sounds like the question's conflating the two. That is, most casters deliver touch spells by making a touch attack which deals no damage and delivers the spell's effect, but the attack roll is made against the foe's touch Armor Class. However, a caster can opt to deliver a touch spell's effect with an unarmed strike or natural weapon which deals unarmed strike or natural weapon damage in addition to the spell's effect, but, in that case, the caster typically makes the attack roll against the foe's normal Armor Class!
A magus employing the supernatural ability spellstrike essentially adds melee weapons to the short list of alternative and more violent ways that touch spells can be delivered (i.e. unarmed strikes and natural weapons becomes melee weapons, unarmed strikes, and natural weapons), and such attacks are usually made against the foe's normal Armor Class rather than the foe's touch Armor Class.