Senator John Forbes Kerry was born in 1943. His father was a diplomat so the family travelled a lot. Kerry went to boarding school in Switzerland and then New Hampshire before studying law at Yale University.
The Vietnam war
In 1966, he joined the US navy and fought in Vietnam where he commanded a river boat in very dangerous waters.
He came back with medals for his bravery, but also with a changed attitude to the war. This was the start of his political career. What he saw in Vietnam convinced him that the war was wrong. He began campaigning in the US for the troops to be brought back home.
The combination of being anti-war, but also a war hero meant John Kerry was in a strong position in the 1960's.
In 1984, Kerry was elected to the US Senate. He's represented the state of Massachusetts for nearly 20 years. That was good for his image but it also caused some problems. During his time as senator, he's voted on loads of different issues.
The Republicans closely examined this voting record, looking for examples where they said he had changed his mind on important issues. They wanted to use those examples to argue that he was unreliable and "flip-floped" by changing his mind on important issues.
Senator Kerry is married to Teresa Heinz Kerry. The name Heinz comes from her connection to the famous tomato ketchup company.