The vice-president's primary duty is to succeed to the presidency in the event of the resignation, removal or death of the incumbent president.

The vice-president's only other constitutional responsibility is to preside over the US Senate and to use his vote as the decider in the event of a tie. This is only overridden when the senate is conducting an impeachment trial against the president.

In recent years, vice-presidents have taken on an increasingly prominent role managing a range of high-profile foreign and domestic policy programmes.