A guide to making your vote count

For only the second time since 1938, a presidential election will ultimately be determined by the second, third, and fourth preferences cast by voters.

Our new president will by no means necessarily be the candidate favoured by the largest number of voters.

Or, to put it another way, for only the second time in those 12 presidential elections will “plumpers” - voters who don’t vote down 2,3,4, etc beyond their Number 1 - potentially forgo the chance to determine who is and who is not elected.

Every preference may count, and every opportunity declined to use a vote effectively, to vote through the list, may also tell in what promises to be a knife-edge election.

The presidential election, like the byelection in Dublin West, is conducted in the same way all Dáil elections are run – by the Single Transferable Vote system of proportional representation, known to one and all as “PR”.

The difference, of course, is in both cases there is only one seat up for grabs in each constituency, and so that mysterious “quota” - the number of votes needed to get elected - is simply half the total vote plus one.

Should any candidate not reach it on the first count, a most likely event, tellers will proceed to count the lowest candidate’s second preferences - and so on until someone is elected.

Since 1938 there have been 12 presidential elections, half uncontested, and half of those contested - 1959, 1966, 1973 - only saw two candidates in the field, making second preferences a non-issue.

Of the other three contests, in two cases, in 1945 and 1997, lead candidates, Sean T O’Kelly and Mary McAleese, respectively, each got over 45 per cent of first preferences cast. Their election was guaranteed on the second count with only the most minimal transfers required.

In 1990, however, like 2011, transfers were/will be crucial to the outcome.

Mary Robinson was behind Brian Lenihan on the first count by 82,000 votes but then swept past him on the second count to win by roughly the same margin when she garnered Austin Currie’s second preferences by a five-to-one margin.

This year, unless the polls are seriously wrong, no candidate is likely to be within ten percentage points of a simple majority on the first count. The election, with seven in the race spread out the way they appear to be, is certain to go to a second count, probably a third and possibly even fourth or fifth.

The ultimate winner will be the candidate who marshals enough second, third, and even fourth preferences.

Voters who want to do everything they can to ensure a specific candidate is not elected should use their vote as effectively as possible, by placing a 7 opposite their most disliked candidate and 1,2,3,4,5,6 opposite the others in whichever order appeals.