It changed, mainly with Nixon, My folks used to get the Post and the Star, the latter was more conservative in its outlook. Later they got the Baltimore sun instead of the Washington Post. I'd read both, and make up my mind, but the Post went off the rails some time during the Nixon Administration.
I think the WashPo was always left of center, but in the 1980s it was only moderately left of center, generally, and had still not gone over to the dark side of suppressing the truth for the sake of a political agenda. Their bias was there, but it was more acknowledged.
Then again, back in the early 1980s, I wasn't an avid political reader of any paper, either.
Also, back in the early 1980s, at the beginning of my misspent yout', I was more liberal than I am now in certain respects.