Final answer:
Barack Obama had the highest percentage of voter turnout in the US election.
Step-by-step explanation:
The candidate in the US election that saw the highest percentage of voter turnout was Barack Obama in the 2008 presidential election. According to the provided information, voter turnout rates were highest for voters age 65 and over. However, race and ethnicity can also influence voter turnout, with White people historically turning out to vote in the highest numbers.