Bush was not really that liberal, he was a moderate conservative who seemed liberal compared to Reagan. He was anti-busing, pro-deregulation, pro-death penalty, pro-military buildup, anti-gun control, anti-price controls on oil and gas, pro-welfare cuts, and whatever he said about “voodoo economics,” favored a $20 billion supply side tax cut. He was also not really pro-choice:
“
FEDERAL FUNDING OF ABORTION: I am personally opposed to abortion. I am also opposed to a constitutional amendment which would override the Supreme Court decision by totally prohibiting abortion because there is a need to recognize and provide for exceptional cases -- rape, incest, or to save the life of the mother. I oppose federal funding for abortion, with the exceptions noted above.”
http://www.4president.org/brochures/1980/georgebush1980brochure.htm
Compare that to John Anderson, who was still able to come in 3rd place in the Republican primaries, and who:
— was for Affirmative Action
— was for busing
— was against draft registration
— was against military buildup
— “marched in the streets for abortion rights”
— said “It’s about time the Republicans had a peace candidate,” and compared himself to Gene McCarthy (!)
The differences between Bush moderation and Anderson liberalism were apparent at the time. Wrote the Atlantic:
“His problem is that Baker and Bush, particularly Bush, have corralled most of the moderate wing of the Republican party. There are strong differences between Anderson and Bush/Baker on such issues as SALT, defense spending, and energy, but Anderson has not been successful at exploiting them.”
http://www.4president.org/brochures/andersonlucey1980brochure.htm
https://www.theatlantic.com/magazine/archive/1980/02/john-anderson-the-nice-guy-syndrome/306028/
And in the Senate, people like Charles Mathias, Chuck Percy, Lowell Weicker, John Chafee, Jacob Javits, and Mark Hatfield represented a kind of Republicanism that was more liberal than Bush’s in this era.
In short, he could be a lot more liberal! He just couldn’t have been more liberal and had much success as a presidential or vice presidential contender.