Unlike many, politicians have to re-apply for their jobs every four or five years and the decision about whether they should be re-appointed is in the hands of voters.
And voters can be rather unpredictable and prone to switch allegiances, as the recent county council election showed rather dramatically.
So, we should not be surprised that a number of Conservative backbenchers in the county voted last night for the 'rebel' amendment on the Queen's Speech.
There is nothing like a bruising mid-term electoral lashing to concentrate the mind and the Kent MPs who backed the amendment no doubt had given careful consideration to the dramatic UKIP surge in the county council election.
So, this was a convenient way of sending a message to the electorate that they are as sceptical about Europe as any UKIP candidate who might be on the ballot paper in 2015.
Their decision to blow a raspberry at Mr Cameron will prove particularly helpful in election literature to post through doors in a couple of years.
Conservative backbenchers in Kent know that the issue of Europe is not going to go away. Those who knocked on doorsteps during the recent election campaign found that Britain's membership of the EU and immigration were often not far from voters' thoughts.
While UKIP is unlikely to win Parliamentary seats at the next election, that is not the point. It is whether UKIP will cost them votes in sufficient numbers to lose them their seats.
Marginal seats like those in the Medway Towns, north Kent and Thanet have switched between Labour and the Conservatives over recent years and if there is one thing that current MPs fear it is that a split in the vote for the right will allow Labour back in.
Whether UKIP's surge will be durable is, of course, open to question.
But if the results of the recent election showed anything, it is that voters are deeply cynical about commitments made for some time in the future - and particularly cynical about promises to do things after the election.
MPs who backed the rebel EU amendment understood this. It might be considered gesture politics but it is inconceivable that they did not make a calculated decision that it was worth putting a marker down now - even if the election is two years away.