This will be my last column for The New York Sun for some time. I’m going back to work for Rudy Giuliani, as communications director and senior policy adviser for his political action committee, Solutions America.

I’ve been at the Sun since its launch, four years ago, and I have loved being a newspaper columnist, particularly for the Sun. Before that, as many readers know, I spent four years working for Mayor Giuliani. I started out as an advance man for his 1997 campaign, one year out of college, and worked my way up to eventually serve as his chief speechwriter. It was an exciting and formative time, shaping my perspectives on politics, policy, management, and leadership. I was able to watch up-close the processes his team used to turn around the city where I was born, which I’d seen from the burnt-out lots and civic decay of the 1970s to the summers of Tawana Brawley and 2,000 murders.

It was the attacks of September 11th that were the defining experience of my life to date. I was at City Hall during the World Trade Center collapse and spent the next three months with my team of three – Owen Brennan Rounds, Mark Ribbing, and Matt Lockwood – writing eulogies for all the fallen firefighters and police officers. It is the kind of experience that sears its imprint on your soul. It sharpens your perspective and deepens your resolve.

I see this new transition as a continuation, not only of my time at City Hall but as a continuation of the good fight helped wage from these pages. Just as I’ve always felt that politics is purposeful because it gives you the chance to participate in history in the present tense, journalists and columnists famously feel that their real compensation comes with writing the first draft of history. In addition, because of my background in government, I’ve always looked at my newspaper column as another way to get things done. I have had three rules for my column: be fair, don’t stoop to character assassination, and try not to criticize without offering a solution.

I also approached my column as a way to update the political perspective expressed in my book “Independent Nation: How Centrists can Change American Politics,” aiming to be a strong advocate for the center during a time in which it has been under attack by bitter partisanship and self-reinforcing polarization in both politics and the press. Some people view politics as winner-take-all ideological blood sport; I have a different idea about democracy. In my view, as we face a war between freedom and fundamentalism abroad, we do not have the luxury of dividing ourselves into warring camps of us-against-them at home. In the current environment, this perspective has been considered contrarian, and if at times this bit of blowing in the wind seemed stubborn, there are signs that the winds are shifting and a backlash is brewing. It is a good time to get off the sidelines.

I’ve written many times that 2008 is shaping up to be a historic moment in American politics, one of those elections like 1912 or 1980, where both parties are engaged in a struggle for their souls and generational political realignment is the result. The opportunity to participate in that process first hand is too great to pass up.

To be clear, Solutions America is not a presidential campaign. It is part of Rudy Giuliani’s determined effort to elect Republicans in the 2006 mid-term elections. But the issues at the forefront of this election and on the horizon – winning the war on terror, restoring fiscal responsibility, and reviving a more unified approach to problem-solving in Washington – are consistent with the goals I have tried to advance in this column. It just does so in another arena, under the leadership of someone for whom it is an honor to work – not just America’s Mayor but a very human American hero, at a time when we could use more real heroes in public life.

Every ending is also a beginning, and I do not know when I’ll return to my column. I hope and trust that my principles will remain the same throughout. I want to thank the editors, investors, and fellow writers at the Sun, as well as the readers who have expressed appreciation for my work – along with the invigorating and amusing bit of hate mail – in letters and e-mails and occasionally stopped me on the street or in the subway. Together, I think we’re finding that America’s largest city enjoys an unpredictable, thoughtful, center-right, broadsheet newspaper.

So as I leave a job I’ve loved for another challenge, I think of a favorite quote from Theodore Roosevelt – another New York reform Republican – the one about “the man who is actually in the arena; whose face is marred by dust and sweat and blood … who, at worst, if he fails, at least fails while daring greatly. Far better it is to dare mighty things, to win glorious triumphs even though checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much because they live in the gray twilight that knows neither victory nor defeat.”