In Jeff Zucker’s announcement on Friday that he was stepping aside as the head of NBC Universal, Comcast’s purchase of the company was taken almost as a fait accompli.

But the combination of NBC and Comcast is still undergoing government review, and Comcast has poured out its piggy bank in Washington to see it through, spending tens of millions of dollars on lobbyists, donations, ads and investments. That spending has recently become a talking point for opponents, who say that Comcast is effectively trying to buy government approval for the deal.

“It’s a big, expensive example of machine politics,” said Susan P. Crawford, a professor at the Benjamin N. Cardozo School of Law at Yeshiva University, who is writing a book about the proposed merger. “You hire all the lobbyists and lawyers in town; you hand out contributions to every politician you can think of; you buy the affections of every group that might complain about the merger, and you strike fear in the hearts of anyone who will need to do business with you in the future.”

She added, “It’s about as subtle as a wet fish in the face.”

Comcast counters by saying that such steps are common when companies are facing regulatory approval in Washington. It says the merger is pro-competitive and in the public interest, promising fuller access to TV shows, movies and news. A recent full-page ad in The Washington Post featured a smiling young couple and the quote, “More ways to enjoy our TV, computer and even mobile devices? Sounds good to me.”