I've seen it stated frequently that large campaign contributions are used, especially by corporations, to buy the influence of a politician. Many places have gone so far as to say that corporate campaign contributions are legalized bribery (and I'm inclined to agree, especially when seeing how these politicians vote). However, this attempted bribery would lose strength if the money must be used for political ads and funding the campaign. (The appeal of bribery is the ability to buy a fancy sports car, nice house, private jet etc., not 'more ads on Facebook')
Are these contributions just cash for the politician, or are they only able to be used for campaigning? For example, if a politician raises $30 Million, and then only uses $25 Million for their campaign, what happens to the remaining $5 Million? Does it go into the politician's personal bank account? Back to the people that donated? To the government? Somewhere else?
If the money can only be used for the campaign and nothing else, what motivation would a politician have to take enormous sums from companies, rather than raising it from voters?