In principle, any of the single-member district systems can be used for the direct election of a president. When a president is to be elected as the executive head of state, there is often a strong normative and practical preference for systems which ensure a victory by an absolute majority. The majority of all countries that have direct presidential elections use a Two-Round system.
The separation of the two rounds leads to efforts by the leading candidates to attract second-round support and endorsement from those eliminated after the first round. Such agreements are sometimes driven primarily by the desire for victory. They are thus perhaps less likely to reflect compatibility of policies and programmes than are pre-poll preference-swapping agreements reached between candidates in preferential systems with a single polling day. In addition, presidential elections held under TRS increase the cost of elections and the resources needed to run them, and the drop-off in turnout between the first and second rounds of voting can often be severe and damaging. For this reason, other options such as the Alternative Vote and the Supplementary Vote are increasingly being examined.
