WASHINGTON (CNN) -- Focus on the Family Chairman James Dobson will sit out the 2008 presidential election if former New York City Mayor Rudy Giuliani is the Republican presidential nominee, he writes in an editorial posted at http://www.worldnetdaily.com. Dobson was specifically critical of Giuliani's position on abortion and marriage as well as the former mayor's three marriages.

"Is Rudy Giuliani presidential timber? I think not," Dobson wrote. "Can we really trust a chief executive who waffles and feigns support for policies that run contrary to his alleged beliefs? Of greater concern is how he would function in office. Will we learn after it is too late just what the former mayor really thinks? What we know about him already is troubling enough."

Dobson attacked Giuliani for publicly saying that "hates" abortion but supports a woman's right to have one. Giuliani had been criticized for being ambiguous on his abortion views, but firmly stated last week that he is pro-choice. Giuliani has said

"Rudy wanted conservatives to believe he had undergone some kind of an election-eve conversion, more or less," Dobson wrote. "Then the contradictions began catching up with him, which often happens to those who play games with words. No, this leopard has not changed his spots."

As for Giuliani's three marriages, Dobson wrote that there are "moral concerns about Giuliani's candidacy that conservatives should find troubling."

"I cannot, and will not, vote for Rudy Giuliani in 2008," Dobson concluded. "It is an irrevocable decision. If given a Hobson's -- Dobson's? -- choice between him and Sens. Hillary Clinton or Barack Obama, I will either cast my ballot for an also-ran -- or if worse comes to worst -- not vote in a presidential election for the first time in my adult life. My conscience and my moral convictions will allow me to do nothing else."

Maria Comella, a Giuliani spokeswoman, pointed out that Giuliani is aware that his views on abortion may cost him some votes, but that he respects those that disagree with him.

"From the beginning, Mayor Giuliani has been straightforward on where he stands on the issue," Comella said. "It's a sign of leadership to stand by your views in the face of political expediency."