Using open secrets data does not even begin to cover the ways in which a company can influence politics.
That sounds almost sensible until one realizes then when you say using their search monopoly what you mean is using the money they make from search.
By that logic NO profitable business would ever be able to move into another line of business. Also, that isn't what anti-trust law is about.
Actually anti-trust law is about using the profits from one business to vertically integrate others by using the profits from one to subsidize the other. There is a modern component to it that revolves around consumer harm but anti-trust law was written as a means of redress for other businesses.
http://en.wikipedia.org/wiki/Standard_Oil#Monopoly_charges_a...
1) Google does make political donations, but they are quite small (~$5000 per candidate) and primarily towards candidates who - to generalize greatly - are "pro internet" (eg anti-SOPA etc)[1][2][3]. One could argue that these people also generally have a "hands off the internet" approach to internet policy which is favourable to Google. One could also argue that a a "hands off the internet" approach to internet policy is sensible..
2) Based on your comment If giving a browser away is anti-competitive I wonder what giving an entire operating system + browser away for free is it would appear you don't understand what anti-competitive behaviour is or what happened in the MS case. A company can give away anything they like - it only causes legal problems if they have market dominance in that market and they use that dominance to exclude other competitors. Microsoft didn't get in trouble just for making IE free - they got in trouble for stopping PC manufactures installing Netscape on new PCs if they installed Windows and for manipulating the Windows APIs to favour IE over Netscape.[4]
[1] http://thehill.com/blogs/hillicon-valley/technology/244593-g...
[2] http://www.google.com/publicpolicy/transparency.html
[3] http://static.googleusercontent.com/external_content/untrust...
[4] http://en.wikipedia.org/wiki/United_States_v._Microsoft