Vote splitting

What hap­pens if a con­stitu­ency has a large num­ber of can­did­ates? Do the votes get split, with the win­ner win­ning with a lower mar­gin?

For ex­ample, if there are sev­er­al hun­dreds of can­did­ates like at Nalgonda or Belgaum in 1996, do the win­ners tend to win with re­l­at­ively low mar­gins? Is the CPI’s 9% mar­gin at Nalgonda or JD’s 11% mar­gin at Belgaum re­l­at­ively low?

2004-winnersLet’s con­sider the 2004 elec­tions. Here is a plot – each dot in one con­stitu­ency, show­ing the winner’s mar­gins again­st the num­ber of can­did­ates. It also has a blue line through the middle show­ing the be­st straight line that fits the data.

What we find is that when there are more can­did­ates, the mar­gin for the win­ner ac­tu­ally in­creases slightly, rather than re­du­cing. It’s al­most as if the in­creased num­ber of can­did­ates con­fuses the voters and drives them to­wards the lead­ing or strongest can­did­ate. In any case, the winner’s mar­gin is cer­tainly un­af­fected by an in­crease in num­ber of can­did­ates.

2004-runnerBut what about the oth­er can­did­ates? Do the runner-ups see their mar­gins de­clin­ing? That is, does the dif­fer­ence between the 2nd and 3rd can­did­ate shrink as the num­ber of can­did­ates increase?From the graph along­side, the an­swer is a re­sound­ing yes. The runner-up mar­gin takes a big hit when there are more can­did­ates.

So at least in 2004, in­creas­ing the num­ber of can­did­ates was a good strategy for the party that has a strong can­did­ate.

What about for oth­er years? In 2009, the pat­tern is sim­il­ar. The win­ner mar­gin dipped mildly with in­crease in num­ber of can­did­ates. The runner-up mar­gin dipped dra­mat­ic­ally with an in­crease in mar­gin.


In fact, in a num­ber of elec­tions, this pat­tern was stronger, for ex­ample in 1977, 1984 and 1989.


However, in the 1980 elec­tions, the num­ber of can­did­ates im­pacted the win­ner and runner-up mar­gins equally. The 1951 and 1957 elec­tions showed a sim­il­ar char­ac­ter­ist­ic.


In re­cent times, an in­crease in num­ber of can­did­ates ap­pears to fa­vour stronger can­did­ates. It may, in fact, be a vi­able lead­ing party strategy to in­tro­duce more can­did­ates in­to the elec­tions to split the votes of the runner-up, en­sur­ing a stronger win.

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