Merlot has gotten a ton of hate ever since Sideways (the movie which extols Pinot Noir and hates on Merlot) came out, but it is definitely the dominant grape in Bordeaux.Interesting, as I would not have thought Merlot would be the largest share.
In Bordeaux the "Left Bank" wines are typically Cabernet Sauvignon dominant, balanced with Merlot. Right Bank wines are generally Merlot dominant, balanced with less Cabernet.