Kerry, who is opposing President George W. Bush in the race for the White House, said he believes the race is close and there are a number of important issues depending on it, adding, "The Supreme Court of the United States is at stake."
None of the nine members of the high court appears to be retiring soon, and all have selected clerks who would serve through the probable end of the current term next June.
Whoever wins the presidency would get to select their replacements, subject to Senate confirmation.
Replacing three justices would tip the high court either to the right or to the left on issues such as abortion and affirmative action.
2014: The Year in Music [PHOTOS]