I have a slightly different view. Public opinion isn't that easy to shift, if you define the public as all people eligible to vote. The problem you have in most countries is that isn't who votes. Voting is optional, so only a self selected population votes. It appears to easier to influence voting patterns of that self selected population.
I am not sure how I would characterise the voting intentions of "all voting public" versus "people who choose to vote", except to say they are less likely to vote for radical ideas. Which isn't surprising I guess, as people who don't vote are probably happy with the status quo. If they weren't, they would vote.
Thus in Australia, where it is compulsory to go to the voting booth (although as a practical mater it is not compulsory to vote), there are far less "out there" politicians. Thus in the US a fundamentalist church group organising to political drive to get evolution cast out of schools has more of a hope, as they can get all their members to vote but only 50% of the opposition will vote. In Australia they have no hope, unless the anti-evolution mob truly has a majority. Naturally they don't, and almost certainly never will.
This is probably why the internet filter proposal in Australia failed to get up in the end. There were a lot of very noisy people supporting it. In the US, they might of had a hope. In fact many very poorly thought out internal censorship proposals in the US have made it into law, and would still be there were it not for your constitution. In Australia we don't have such a strong constitution. But such proposals have no hope because they are up against the silent majority, and that is because in Australia the silent majority are forced to make their opinions heard at the polling booth.