Moreover, Mr Portman comes from the vital swing state of Ohio, and veepologists in the media pay extravagant attention to electoral geography.

ECONOMIST: Lexington

Thanks to the vagaries of electoral geography, in recent elections Labour MPs have required many fewer votes to win, on average, than Conservative candidates.

ECONOMIST: Voting reform

Moreover, Scotland's electoral geography means that Labour, unlike other parties, cannot use the introduction of proportional representation to even up the numbers of each sex.

ECONOMIST: Scottish politics