Partial results in Liberia's presidential election show Nobel Peace Prize winner Ellen Johnson Sirleaf, the incumbent, is likely to face a run-off vote with her nearest rival.She won 44.5% of the votes while rival Winston Tubman garnered 26.5%, the election commission said.In third place is ex-warlord Prince Johnson with 13.5%, which places him in the position of surprise kingmaker.This is Liberia's second presidential poll since a civil war ended in 2003.If no candidate scores an overall majority, a run-off between the two front-runners will be held early next month.Prince Johnson's forces infamously filmed the execution of dictator Samuel Doe in 1990.President Sirleaf, who was first elected in 2005, was awarded the Nobel Peace Prize last week - a decision denounced by Mr Tubman and other candidates.