Ah, but the retorter isn't giving enough credit to the savvyness of politicians! Sure, candidates may take similar positions due to a genuine agreement, but is that agreement not just as often a result of adopting an already popular opinion? From their point of view, the political landscape is all about compromise and calculated, strategic moves. Taking the time to analyze public opinion data can be an efficient way to do this.
So, it's not so much a collective understanding of the public's opinion as it is using that understanding to one's advantage. Just like companies competing for economic success adopt profit-improving technology, the astute politician adjusts their talking points to climb the political ladder. It is a matter of economics, after all - just different kinds of currency, like votes and public approval instead of profits!
Of course, we can't ignore the possibility that candidates may actually have had similar opinions prior to a popular opinion emerging. But, you have to admit, if one candidate jumps on a bandwagon, they are more likely to benefit from the momentum it carries! If a great idea is floated - like free healthcare - why not grab onto it and hang on tight? Either way, it's good form, and that's what matters in the political game.