It seems like many elected leaders these days are expressing this type of sentiment. The most blatant comes in the form of something like, "we won, you lost, shut up." A more subtle example is how, at town halls, if someone says they are a Republican, their criticism is responded to more earnestly, while someone who doesn't identify their political affiliation is automatically dismissed, even if they have a similar criticism. I saw Lindsey Graham, for instance engage in versions of both types of expression.
Where did the belief that seems to indicate that politicians only represent people who voted for them come from? Is it new, or has it just gotten worse? If there were times in history when polticians sought more consensus, what do you think were the conditions (electoral system or otherwise) that better facilitated that kind of discourse? How were those conditions put in place?
It absolutely isn't new. Look at Edmund Morgan's work, Inventing the People, you can see how American ideas of democracy, liberty, freedom etc, developed from British to colonial times.
Is it worse now? As a historian I would say that nothing is new. There have been times throughout American history where both parties were more compromising than at other times. Why? There are many factors, but I think the primary factor when parties are more prone to compromise is that there is not a giant issue that divides the nation, slavery for example.
You can see how the political parties treated one another, yes there was more genteel respect in the past, but on the other hand you also have the Caning of Senator Charles Sumner by Rep. Preston Brooks. https://www.senate.gov/artandhistory/history/minute/The_Caning_of_Senator_Charles_Sumner.htm
I'm not sure the last time I heard in the news cycle of members of Congress beating each other.