McCain has been going on and on about how Obama's plan to give tax relief to Americans not already paying taxes amounts to socialism or "welfare". In essence, the poor and lower-middle class, because they pay little to nothing in taxes (because they're poor!) should get no relief at all. Instead, the richest Americans should get $100s of thousands, or millions in tax credits, while the poor get nothing.
Interestingly, the exact same criticism applies to his corporate tax plan, which creates new credits and reduces taxes, pushing some corporations that currently pay little to no taxes into getting a check back from the government.
In effect, McCain's corporate tax proposal sends checks to large corporations that are currently paying taxes. Like the bailout, it's fine when applied to big corporations, but "socialism" when applied to hard-working, impoverished Americans.