SAN FRANCISCO -- After delivering a textbook example of how to nail a set of talking points during a high-profile Friday press conference on Proposition 1A -- the high speed rail initiative -- San Francisco Mayor Gavin Newsom used a PolitickerCA.com question to articulate why principles mean more to him than political gain.

In a wide ranging answer to a question about his thoughts on the status of Proposition 8, the ballot measure that would ban gay marriage in California, an unprompted Newsom explained why the fate of the measure and of gay and all civil rights means so much to him.

Although he said he remains cautiously optimistic that Prop. 8 will be rejected by the voters on Tuesday, Newsom worried the fallout from a successful outcome for the measure would forever damage the Golden State's tolerant and forward-thinking reputation.

"California (is) a state that has always prided itself on thinking out five, 10 or 20 years into the future. We would be the first state in the nation to take rights away from same sex couples by changing the constitution. If it happens it will be a pretty remarkable thing. If the proponents win on this, I suspect the post-election analysis on this will be pretty damning...."

Newsom, who has launched a gubernatorial exploratory committee in what may become an effort to succeed Gov. Arnold Schwarzenegger in 2010, then offered some personal reflections on why as a heterosexual male politician he has become, arguably, one of the leading advocates for gay rights and same-sex marriage in California, if not the nation.

"Look, I'm going to fight for what I believe in. ...I am not one of those guys who checks the polls before I check my gut. This issue (Prop. 8 and gay rights) is not really a favored one even among members of my party. Even though privately they're telling me one thing, publicly they won't say it because it won't help their political careers. I don't care more about my political career than I care about principles that I believe in. That is what matters to me. If I can't run and win another office -- so what? At least I stood up for a principle I believed in. And that's the rest of my life. I get to look back and say that I fought for something I believed in and whether I won or lost, I did what I thought was right. That's a hell of a lot more important to me to be there at (age) 75 or 80 ... (than) saying I was the ex-governor of California. Big deal. Or the ex-senator or the ex-mayor. Who cares? That's pretty trivial."