Fifty years ago Richard Nixon was the president and both legislative bodies were controlled by Democrats. However, fifty years makes quite a difference and the MC-Index for this session exposes just how diverse the parties were ideologically.
The Republicans
The highest scoring Senate Republicans were Barry Goldwater and Paul Fannin of Arizona as well as Karl Mundt of South Dakota, who got 100%. The lowest scoring Senate Republican was Clifford Case of New Jersey, who scored a mere 8% this session. President Richard Nixon scores a 72%, five points above the average Republican score of 67%, while Senate Minority Leader Hugh Scott of Pennsylvania scores a 52%. In the House, the average is a 76%. The ones who scored 100% are
H. Allen Smith, California
Phil Crane, Illinois
Charlotte Reid, Illinois
Earl Landgrebe, Indiana
David W. Dennis, Indiana
Durward G. Hall, Missouri
Samuel Devine, Ohio
George Goodling, Pennsylvania
LaMar Baker, Tennessee
Bill Archer, Texas
William Scott, Virginia
The lowest scoring was Ogden R. Reid of New York, who scores a mere 6%. It is no surprise he switched to the Democrats in 1972. President Richard Nixon scores a 76%. House Minority Leader Gerald Ford scores a 78%, slightly above the average.
The Democrats
The highest scoring Democrat for this session was John C. Stennis of Mississippi, who scored an 87%. The lowest scoring Democrats were Harold Hughes of Iowa, Edmund Muskie of Maine, Ted Kennedy of Massachusetts, Phil Hart of Michigan, Walter Mondale of Minnesota, Harrison Williams of New Jersey, Fred Harris of Oklahoma, and George McGovern of South Dakota who all scored a 0%. Senate Majority Leader Mike Mansfield of Montana scores a 20%. The Democrats who scored a 0% in the House were
Morris Udall, Arizona
Ron Dellums, California
Don Edwards, California
Gus Hawkins, California
Patsy Mink, Hawaii
Abner Mikva, Illinois
John Culver, Iowa
Parren J. Mitchell, Maryland
Charles Diggs, Michigan
Donald Fraser, Minnesota
Robert Bergland, Minnesota
Shirley Chisholm, New York
Bertram Podell, New York
Herman Badillo, New York
John G. Dow, New York
Louis Stokes, Ohio
William J. Green, Pennsylvania
Bob Eckhardt, Texas
Bob Kastenmeier, Wisconsin
The highest scoring Democrat is James A. Haley of Florida with a 98%, and Democrats average 33%. Speaker of the House Carl Albert of Oklahoma, who voted an unusually high number of times this session scored a 24%.
Although ratings for this session of Congress won’t be out until after 2022, I can promise you on average the Democrats will not score a 33% and I don’t think Chuck Schumer or Nancy Pelosi at any point have had their MC-Index score in the twenties. Mitch McConnell I can tell you has never scored as low as a 52% and for Kevin McCarthy, well he may have scored a 78% or below in a session or two. Although Republicans were still the more conservative party, the Democrats had some genuine staunch conservatives on their team, like Republicans had some real liberals on theirs. For better or worse, the project to create two ideologically responsible parties has indeed succeeded.
The files for House and Senate, respectively:
Mad Politics: The Bizarre, Fascinating, and Unknown of American Political History 
I noticed that among the GOP representatives you said got a 100% score for the 92nd Congress include Charlotte T. Reid, who represented a suburban Illinois district. Would you happen to know if she was overall strongly conservative or moderate-leaning? There’s also her vote against the final passage of the Civil Rights Act of 1964, which I don’t know the exact reason behind. Interestingly enough, she supported the initial House passage of the bill. Reid also voted for the Voting Rights Act of 1965 and the Civil Rights Act of 1968.
Reid thought of herself as a conservative Republican and Americans for Constitutional Action agreed, having her at a life score of 91% and in 1971 her score comes out at 82%. The only reason her score is even that low is that the ACA counted a few odd votes during the Nixon years, including a compromise agriculture bill in 1970 and a vote to increase NASA funding after the moon landing. NASA historically had both conservative and liberal supporters and critics, and this was a rather strange include as this appears to be the only NASA vote they ever included on their grading scale. However, she definitely did compromise during the Nixon Administration, with her voting for foreign aid and Nixon’s Family Assistance Plan in 1970. The latter was especially jarring as twenty years before the idea of any more than a small band of liberal Republicans supporting guaranteed minimum income was unthinkable, but a majority of Republicans voted for it in 1970. Thanks, Nixon!
There are also three votes ACA counts that I didn’t for 1971 that bring her score from 100% to 82% and all three fail my test for inclusion as a majority of conservative and liberal extremists voted against these. The first is a debt limit vote, which often are not much more than opportunities for opponents of an administration to bash it on spending and I don’t find it that useful in determining ideology. I prefer counting proposals for budget cuts or discretionary spending measures. The second is a bit of an odd bird that’s over a railway management dispute. The third is the Lockheed Martin bailout. That’s a pity as I would have liked to do the third as an example of conservatives opposing bailouts, but there are others that do make my scale, including the 1970s railroad bailouts, the Chrysler bailout in 1979, and the Wall Street and auto bailouts in 2008.
Reid was one of six representatives who changed their minds on the Civil Rights Act of 1964 between the House bill and the Senate bill. I remember reading somewhere, although I can’t find the source at the moment, that she and the two others who switched from support to opposition were reluctant in voting for the House bill and had done so hoping it would be improved to their satisfaction in the Senate, meaning made more mild, and it wasn’t.
Ah, good detailed analysis. I remember wondering to myself when first examining the roll call vote for the final House passage of the Civil Rights Act of 1964 why the Republicans who voted “nay” decided the way they did. And I also didn’t know before that her conservatism was this strong. I previously got the impression that she could be considered both a conservative and a Moderate Republican to a certain degree, given her support for the Equal Rights Amendment, which activist Phyllis Schlafly led a grassroots movement in defeating. I furthermore would be curious as to what Reid’s position on abortion was, if such was ever documented.
Thanks! Yeah, abortion was a bit after Reid’s time in Congress as she resigned in 1971 to accept a position as an FCC commissioner and Roe v. Wade was in 1973. I believe the ERA itself would absolutely be in the Constitution if Democrats weren’t gung-ho on using it as a backdoor to kill the Hyde Amendment and possibly secure abortion on demand as a Constitutional right. These are real possibilities without an abortion neutrality amendment, which they are not willing to have added. The vote for it before that decision was far more lopsided than the 19th Amendment and even won the votes of such hardliners as Phil Crane of Illinois, H.R. Gross of Iowa, and Durward G. Hall of Missouri. The votes were far more contentious on extending the deadline in 1978, reviving it in 1983, and the 2020 vote to remove the deadline acting on the dubious idea that Congress can undo the deadline from the early 70s amendment rather than having to start the process again.