In an ideal world where political horse-trading is far less influential, voters can effectively assert what they want on the March 24 election. In other words, the 250-strong Senate can be taken out of the equation when installing the new prime minister is concerned, although the chamber is provisionally empowered to have a say in the appointment.

The Democrat, Bhumjaithai, Chartthaipattana and Chart Pattana parties form a powerful group of variables in the upcoming Thai election. They, or some of them, will become a decisive kingmaker if neither of the Palang Pracharat and Pheu Thai parties fail to win enough seats in the election to form a government by their own.

The first “ideal” scenario has Pheu Thai and its associates win a combined majority in the House of Representatives. Supposing they manage to win 251 seats, the “swing parties” or some of them will join the alliance, citing “voters’ wish”, and push it past the 376 seats (votes) required.

Pheu Thai managed to win 265 seats in the last election. It was able to form a single-party government, but it declined that option in order to create a strong ruling coalition. This time, the party and its associates will need to repeat that feat to swing the “swing” group.

The second “ideal” scenario is for newly-founded Palang Pracharat to do particularly well in the election. It does not need to become the biggest party, a status monopolized by Pheu Thai, thanks largely to its domination of the populous North and Northeast. If Palang Pracharat emerges an impressive second after the election, with the Pheu Thai camp unable to score a convincing victory, the “swing” parties will be able to side with Palang Pracharat, citing voters’ will.

The first scenario renders the Senate completely redundant. The second one will most likely still need its votes, but a subsequent government will not be prone to harsh attacks at the early stages.

They are “idealistic” scenarios, though. What can happen is that Pheu Thai and associates will still end up in the opposition bloc despite winning the House of Representatives majority, or Palang Pracharat will fall flat despite winning a high number of seats.

In not-so-ideal scenarios, horse-trading comes into play. One or more of the swing parties will make a crucial decision based not on what voters suggest they want, but on which of the rival camps offers the best incentives. For example, one camp can make it past the 376 votes required by dangling the Finance Ministry or the Agriculture Ministry in front of the swing group.

Horse-trading can be of an unprecedented scale if the Palang Pracharat camp, backed by the Senate, and the Pheu Thai alliance are close in numbers. Analysts have not ruled out a leader of one of the swing parties managing to “steal” the premiership. Democrat leader Abhisit Vejjajiva has not been counted out. The same goes for Bhumjaithai leader Anutin Charnvirakul.

Voters can make post-election circumstances easy or tough. A clear-cut verdict may be able to make the swing parties behave properly. An ambiguous verdict, on the other hand, can let them loose and trigger nasty horse-trading.