This post from 2008 takes it farther than I would have been capable of, so hats off and a laurel wreath (with permission from the laurel, of course) to the wit only known as "Writer the Geeklette."
[The Geeklette's post is a tongue-in-cheek apology for making the comparison previously.]
John Kerry and Treebeard are, certainly, not alike. In fact, there are a few glaring differences between the two:
First, John Kerry is a tall, lanky human being. On the contrary, Treebeard is a tall, lanky member of the Ent clan of the Fangorn Forest, encased around the River Entwash.
John Kerry is a wounded Vietnam Veteran and a recipient of the Purple Heart after bravely enduring gunfire while captaining a Swift Boat. Treebeard, on the other hand, awakened the Huorns who decimated an entire army of orcs during the Battle of Helms Deep.
John Kerry has an intelligent, well-traveled wife. Treebeard, unfortunately, lost his wife along with the other Ent Wives after they crossed the River Anduin in search of better fruit pastures during the First Age of Middle Earth.
John Kerry is known as a nuanced speaker who parses his thoughts carefully. Treebeard, on the other hand, spoke Entish, and anything spoken in Entish is only worth spoken when one takes the time to speak it.