THE W hotel chain is aggres sively laying claim to the letter W, no matter what President Bush's nickname is. The group behind the chain, Starwood Hotels & Resorts Worldwide Inc., has fired off legal let ters to two political merchandisers, de manding they re move the letter W — as in George W. Bush — from "apparel and accessories" they are selling. The of fending items include baseball hats and T-shirts "that mimic the trade dress of the W hotels, which has the effect of eroding the unique brand identity developed in the W logo."