If money is mandatory to run for office, what is it mandatory for?

[reddread]

Yard signs? bumper stickers?
TV spots?
that is one of the top contenders for me, but why?
Why did Archer Daniels Midland, the Carlyle Group and Exxon Mobil fund public affairs programming when the spotlight shone?
because they need public support to keep sucking the treasury dry, polluting the ocean and screwing up
our food supply?
or is it more beneficial to purchase silence?
Is that why major, "serious" candidates need more money for their own campaigns than entire elections used to cost?
or are they putting that money to work helping people besides themselves? Paying precinct walking volunteers maybe?
Just wondering.

[unblock]

1. paid media spots, mostly. plus the threat of even more paid media spots to intimidate challengers.

no doubt there is also the "buying" of endorsements and other forms of political help via helping out other campaigns.