Dear Mark,

I wanted you to be one of the first to know: on Saturday, I will hold an event in Washington D.C. to thank everyone who has supported my campaign. Over the course of the last 16 months, I have been privileged and touched to witness the incredible dedication and sacrifice of so many people working for our campaign. Every minute you put into helping us win, every dollar you gave to keep up the fight meant more to me than I can ever possibly tell you.

On Saturday, I will extend my congratulations to Senator Obama and my support for his candidacy. This has been a long and hard-fought campaign, but as I have always said, my differences with Senator Obama are small compared to the differences we have with Senator McCain and the Republicans.

I have said throughout the campaign that I would strongly support Senator Obama if he were the Democratic Party's nominee, and I intend to deliver on that promise.

When I decided to run for president, I knew exactly why I was getting into this race: to work hard every day for the millions of Americans who need a voice in the White House.

I made you -- and everyone who supported me -- a promise: to stand up for our shared values and to never back down. I'm going to keep that promise today, tomorrow, and for the rest of my life.

I will be speaking on Saturday about how together we can rally the party behind Senator Obama. The stakes are too high and the task before us too important to do otherwise.

I know as I continue my lifelong work for a stronger America and a better world, I will turn to you for the support, the strength, and the commitment that you have shown me in the past 16 months. And I will always keep faith with the issues and causes that are important to you.

In the past few days, you have shown that support once again with hundreds of thousands of messages to the campaign, and again, I am touched by your thoughtfulness and kindness.

I can never possibly express my gratitude, so let me say simply, thank you.

Sincerely,

Hillary Rodham Clinton