The article has a link to another excerpt, which actually prints parts of those letters:
Both Sides With John Kerry
Former Democratic front-runner Howard Dean recently criticized current Democratic front-runner John Kerry for taking the wrong positions (by Dean's lights) on both the liberation of Kuwait, which Kerry opposed, and the liberation of Iraq, which he supported. As we all know, Kerry has tried to have it both ways on Iraq, voting "yes" on the October 2002 resolution authorizing war, then proclaiming himself shocked that President Bush actually waged the war Congress authorized.
It turns out Kerry was no less two-faced about Kuwait 13 years ago. The New Republic's blogger Noam Scheiber credits TNR intern Josh Benson with digging up an item that appeared in the magazine's March 25, 1991, issue, quoting a pair of letters Kerry wrote to constituent Wallace Carter of Newton Centre, Mass.:
Jan. 22, 1991: "Thank you for contacting me to express your opposition . . . to the early use of military force by the US against Iraq. I share your concerns. On January 11, I voted in favor of a resolution that would have insisted that economic sanctions be given more time to work and against a resolution giving the president the immediate authority to go to war."
Jan. 31, 1991: "Thank you very much for contacting me to express your support for the actions of President Bush in response to the Iraqi invasion of Kuwait. From the outset of the invasion, I have strongly and unequivocally supported President Bush's response to the crisis and the policy goals he has established with our military deployment in the Persian Gulf."
http://www.opinionjournal.com/best/?id=110004620#bothsides