Is Switching Parties Fair To The Voters?

According to news sources, Democrat House member Jeff Van Drew of New Jersey was/is about to switch from Democrat to Republican, changing the balance there, but not enough to make Nazi Pelosi lose any sleep or brush up on math. But is that fair to his constituents? He is not the first person to switch Party affiliation, and there are those who have gone "Independent" rather than join the other team, but who still feel either betrayed or left behind by theirs. I think when it comes down to it one has to ask whether the voters are voting for the person or the Party. In a perfect world the voters would know their Representative and feel comfortable enough with him as a person to feel that he represented their views and values well enough to be their proxy in Government while they went about their daily business. This would also mean repressing his OWN views when and if they differed strongly from those of his constituents and voting in their stead, and not for what he, personally, desired. One might even expect that if the difference were too strong that he might resign and allow the voters to replace him with someone more in line with their values and thinking. But we do not live in a perfect world.
    Too often the person running for Office misrepresents who he actually is, and he will, once elected, vote in order to stay in power, or, more likely, to gain more power and a better position, say, on a Committee of import. Districts that a politician represents are too vast for there to be a consensus that a Representative can fairly be a proxy for, and, when people DO vote, they often, in a two Party system, simply vote for "their" Party, sometimes not even knowing who the actual candidate is.
  So, is it fair to switch if the voters thought they were voting for a particular Party? No, it's not. But it's also incumbent (no pun intended) on the voters to elect a person, and not simply look at their Party affiliation. A soldier, after all, is expected to refuse an order that blatantly is illegal. If your Party demands that you break your oath to the Constitution, are you not likewise required morally to refuse, even if that means rejecting the Party?