Chris Dillow brings up the well-known puzzle that inconsistency is far more damaging to leaders than it ought to be: politicians are so terrified of being seen to change their positions that it is almost impossible to make a reasoned change.
Their fear is not unjustified; it is forced on them by the voters, who prize "strong" character in a candidate above good decision-making.
The puzzle is why this should be, when the quality of government so obviously suffers as a result.
I imagine it is a holdover from days of stable leadership. As I discussed last year: in the days of monarchies, the worst thing that could happen was that the King would be weak and the state would come to be dominated by competing factions seeking to control him. A strong but stupid or immoral monarch would do less damage. It is very explicit in histories written before the present era, that weak king equals bad king, and strong king equals good king.
It seems that the danger of weak leaders is so deeply ingrained that it survives in the popular mind to this day — even though the demise of monarchy has made it irrelevant. (It may even be innate, but that is speculation). With democracy, you get all the disadvantages of a weak king whether the individual politicians are weak or strong, so there is no good reason to prefer a strong personality over one that is open to reasoned argument.