Vox pop - I know that's two words, but it's possibly what you are looking for. It comes from the Latin "vox populi", meaning the voice of the people.
why is the opinion of the public about a popular movie or television program not a good example of public opinion?
reflects the most popular view of the people
groundswell
You effectively did in your question as I did in this answer. Many writers would argue that the word "effectively" is not a useful word under any circumstance, as in "He effectively was able to change public opinion". Hey, "He changed public opinion", yes or no?
James E. Bradley has written: 'Popular politics and the American Revolution in England' -- subject(s): British Foreign public opinion, Foreign public opinion, British, History, Politics and government, Populism, Public opinion
reflects the most popular view of the people
I think public opinion was just measured by word of mouth unlike today you can measure public opinion by doing something as simple as a poll.
The 1916 Rising was not popular with much of the general public. It was only when the leaders were executed that the opinions changed.
issues of public opinion are related to public affairs
It fell in and out of public opinion throughout his life, but he was generally respected and payed handsomely by the nobility.
public opinion polls
Keep on repeating the same opinion or theme in public as often as possible and before you know it that is the public opinion.