A defeat for the People's National Party (PNP) could signal the political death knell for its president, Portia Simpson Miller, while a Jamaica Labour Party (JLP) loss could see its leader, Andrew Holness, struggling to hang on to his position.
Holness was ushered into the job of JLP leader and prime minister in a surprisingly bloodless leadership change after then party leader and Prime Minister Bruce Golding called it a day in October.
Following Golding's unexpected announcement that he would quit as PM and JLP leader, at least five potential party leaders emerged, including the long-serving Audley Shaw and Mike Henry, the young Dr Christopher Tufton, Robert Montague and Holness.
In the end, back-room talks allowed the others to put aside their leadership aspirations and line up behind Holness with the expectation that the 39-year-old would lead them to a second consecutive term.
A defeat after the votes are counted tonight would mean that Holness has failed to achieve the first major measuring line set by Labourities and would leave him exposed. While he might survive as leader with a defeat, it would be worrying days for the soft-spoken son of St Catherine.
made way through ranks
However, though Holness could fail to lead his party to victory and survive, it is difficult to see Simpson Miller remaining as PNP president if she loses.
The political veteran has made her way through the ranks and came out on top in a bitter race with Dr Peter Phillips, Dr Omar Davies and Dr Karl Blythe to replace P.J. Patterson as PNP president and prime minister in 2006.
After 18 months as prime minister, she led the PNP into the 2007 general election and the party suffered its first defeat in more than 18 years.
That 2007 defeat prompted a challenge from Phillips for the leadership of the PNP in 2008, but again Simpson Miller received the support of the majority of the delegates.
It is likely that a second defeat for the PNP will be the signal for another challenge for the top post in the party, if Simpson Miller does not resign, and this time the challenger could be one of the many bright young leaders in the party.
A PNP defeat could also see other changes in the party with many of the senior officers, including Robert Pickersgill, dubbed 'Chairman for Life', almost certain to be challenged.
It is also clear that either of the two general secretaries, Aundré Franklin of the JLP and Peter Bunting of the PNP, will face unsure futures if their party loses.