Comcast Corporation is bragging of widespread support for its proposed $45 billion takeover of Time Warner Cable, but the victory chant is drowning out an important detail: Some of that support from public officials has followed big campaign contributions from Comcast executives. In a blog post on the company’s corporate website last week, David L. Cohen, Comcast’s executive vice president and chief merger lobbyist, boasted that nearly 70 mayors and more than 60 additional state and local officials have gone on record as proponents of the proposed merger, which would combine the country’s No. 1 and No. 2 cable companies into one massive pay-TV and broadband colossus.