Tanked

[fredpuli47]

Americans say "In the tank" in e.g " The media are in the tank for Obama" meaning "wholly committed to and uncritical of". We might say "In the bag".

A current expression is " to tank" or "tanked" to mean "fail utterly" as in " the economy has tanked".
What's the origin of each of these and what has a tank to do with it?

[dundurn]

I'd assume the analogy is to a petrol tank; in the first case the press are fuelling Obma rather than his opponent, in the second case the tank is empty.