For starters, Roe V Wade was the pivotal point in history when it came to the abortion issue. That is when Americans made up their minds and decided to be pro-life or pro-choice. What Reagan biographer Lou Cannon wrote may not matter to you, however, to pro-lifers what Cannon wrote does matter.
What Ronald Reagan wrote in his own hand, matters even more. Although it was written in 1975, Reagan was referencing his personal struggle with the abortion issue during the 1967-1968 time frame. In an April 1975 radio address Reagan said:
"Eight years ago when I became Gov. I found myself involved almost immediately in a controversy over abortion. It was a subject I'd never given much thought to and one upon which I didn't really have an opinion."
Reagan went onto say, he did extensive research on abortion and "I did more studying & soul searching then on any thing that was to face me as Gov".
"I know there will be disagreement with this view but I can find no evidence whatsoever that a fetus is not a living human being with human rights."
These Reagan quotes can be found on pages 380-385 of the book, "Reagan In His Own Hand". Once again, clearly Reagan was referring to his opinion on the abortion issue from the 1967-1968 time frame, when he was Governor of California. If you choose not to believe Reagan, so be it. I trust what Reagan said.