Ranked choice voting makes a lot more sense for the Presidency or any executive office where the task before the voters is to pick one person to exercise all responsibility for a period of time. I think it would be far more reasonable to adopt a nationally or statewide aggregated proportional vote to get properly representative legislatures. What ranked choice voting would do for Congressional elections is indeed to encourage third parties and independent voices to run seriously, and enable people who suspect they cannot possibly win voting for these to register their support for them anyway, and then get down to the business of still choosing between the two main parties. We'd be better off than the current system in that third candidates might unexpectedly turn into leading ones much to everyone's surprise; it would inject a certain competitive edginess even to the most "Safe" district elections. But at the end of the day, it will lead to a lot of people voting for something they really want, then regretfully settling for a compromise candidate who is deemed conventionally "electable." Whereas with true PR, people can elect the candidates they want, period. People who are in a hopeless minority in one district can push candidates over the top in another where more people have their viewpoint; people who represent a viewpoint that is so rare it cannot ever be expected to prevail in any one district can band together and elect a proportional number of representatives from across the nation. Ranked choice would be better but PR would be best.
Not so for trying to elect a President! I think the OP simply assumes a necessary Amendment goes through in which a ranked choice candidate must win an absolute majority of the American popular vote, and the whole system of state Electoral Votes is simply abolished. This would make a Presidential race essentially the same as a gubernatorial race writ large if both offices have the same rules.
If we simply take votes as cast OTL and translate them into this alternate system then indeed most elections would presumably go as OTL. But it is really hard to say for sure, because of the freedom that being able to just vote for the one you think is really best first, and only fall back on your second, third or even lower ranking after first registering your true preference will shake things up. People might hope that others will favor the same "long shot" candidate they preferred even though national narrative said these outsiders did not have a chance, and their choice of first choice might change their thinking about lower ranked choices.
For instance the OP suggests starting in 1952. As it happens, Harry Truman had a unique privilege to run for the office in 1952, due to the language of the recent Amendment limiting Presidents to just two terms exempting the current office holder when it passed. But as it also happened, he shared the generally dim view of his prospects of winning everyone else did that year, unlike 1948 where all conventional wisdom decreed he was a dead duck, and yet he won election in his own right anyway. Indeed in 1952 voters will remember other upsets in living memory, such as a certain well respected popular magazine predicting Hoover would beat Roosevelt in 1932--this poll was biased by being conducted by telephone, in an era where ownership of home telephones was skewed toward the rich. In the first election under the new system, people will have a healthy disregard for pundits telling them who is sure to win and sure to lose.
So--will the election of 1952 be a simple binary choice between the Republican and Democratic candidate? If in fact all elections are such, then we have no need of anything as fancy as ranked voting; people simply vote for A or B and one of them, getting a plurality over the other, automatically also have an absolute majority and win, pure and simple. The reason we want more complicated systems is that there are in fact always third party candidates, and in many elections--not most OTL, but many--no one gets a popular vote majority. The purpose of ranked voting would then be to hold an "instant runoff" as it were, eliminating the least performing candidate and transferring their votes to the second ranked candidate their prime voters each selected. With heavily divided first rank votes, this might have to go many iterations. And what if in fact people do not choose to vote for any one candidate with majority votes? This depends on the details of the election rules. Do all voters in all locations of the USA face exactly the same ballot, or will some candidates be present on some ballots but not others? Must every voter assign a rank to each candidate to cast a valid vote, or is it OK for them to just vote for one and leave the others unaccounted for? I would want to exercise my right to assign a value to every one, but a lot of people might not want to be bothered; should we honor that, or penalize it somehow? For instance, suppose the ballot has 9 choices and I rank 5 of them, but leave 4 of them blank. Is that simply a non-vote for the candidates left blank? Consider that in say 1948 I might have no opinion on some very obscure candidates but want to declare that I really really don't want to see Strom Thurmond win, and therefore rank my top 4 that I more or less like 1-4, leave the middle 4 blank since I just don't care about them, or am ignorant of what they stand for and don't want to risk ranking someone I might actually like better than another lower or someone with some views that make even Thurmond look good to me higher than Thurmond. So I leave them blank but rank Thurmond 9. Now however my vote might conceivably be counted toward a Thurmond win, whereas the ones I leave blank cannot benefit from my vote regardless. However we could adopt a policy whereby candidates whom voters leave blank are ranked by the national outcomes of people who did vote for them and filled in for me, so all voters are in effect ranking everyone, only some of them on consensus autopilot as it were. That motivates me to form a ranking opinion of everyone on the ballot since otherwise having it interpolated for me could give the reverse of what I would have wanted had I had time to form my opinions on each. Much can depend on the detailed rules! Who gets to decide which candidates appear on a national standard ballot, and can I write in a tenth candidate and rank them #1?
Let's assume that we do have a single national ballot, and it does not allow for write ins, and voters are free to rank as few or many as they like but practically speaking all do rank the leading candidates somewhere on their list. And the rule is, the President is the one who has 50 percent plus 1 or more votes, something mathematically guaranteed to happen if the iteration eliminates all but the top two, though the majority figure the winner has then might be a much lower number than half the total votes cast. The idea is if you can't be arsed to rank a candidate, your vote just does not count at that stage.
Now the
Election of 1952, if we assume everyone's first choice is frozen to be as OTL, is a big snooze, because Dwight Eisenhower was the Republican candidate, after a period of 20 solid years of Democratic Presidents, with the last couple years of Truman's final term being marred by serious crises he was plausibly blamed for, and the whole Democratic ascendency by association. The Republicans might have run someone less assured of victory than Ike, and still won. Possibly. Looking at the table down in the article collating all the popular votes cast for all the candidates, we find there were not 2 candidates who received PV but eight, including over 9000 out of almost 62 million who went for yet more minor candiates. Assuming the other six minor party candidates had no trouble getting listed on the ballot, and that no other candidates made the cut, and disallowing write-ins, those 9000+ voters would have to choose one of the other 8 for their prime vote.
But the election is a snooze because even counting them, out of a total of 61,751,942 people voting a candidate needs 30,875,972 votes to win--but Eisenhower got nearly 3.2 million votes beyond that, a margin over 10 percent. The count process stops right there and Eisenhower is President by a landslide!
But wait, if people can rank their votes by preference, why should Ike get such a clear comfortable majority out the gate? This is presumably the first election where people do not have to begin by choosing the lesser evil and being done with it. Look at the names of the 6 parties and Presidential candidates trailing behind Ike and Stevenson--5 of the 6 appear to be more or less leftist parties, with Douglas MacArthur getting a very small share of votes under the Constitution banner as the only candidate apparently to the right of Eisenhower. Conceivably the Prohibition party might be more reactionary, but given the history of the Temperance movement OTL I think that would be a hasty judgement--one would have to look into it carefully. Had all of those voters, and the 9000+ for yet more candidates, and even those for MacArthur all concentrated on Stevenson--he'd still lose. But what if people who felt they had to choose between Stevenson and Eisenhower could first exercise a much broader discretion, only coming home to the two mainstream parties after registering the exact character of their dissent?
It also seems reasonable a lot of people who voted for Ike OTL would first vote for MacArthur if their second choice brought them into Eisenhower's fold safely. I think everyone who did vote for MacArthur could be counted on to prefer Ike over any of the other choices except maybe Prohibition, and assuming Prohibition gets no more than a factor of 10 bump overall, the initial rank votes might look extremely different; conceivably MacArthur gets more than half the votes Ike did OTL, reflecting the conservative base of the Republican party, and ranks first of all candidates, while the left wing vote overshadows the right with people who ultimately back Eisenhower first weighing in as say for the Progressive party, along with a lot of Stevenson OTL voters first favoring the various socialist/progressive parties too.
The whole point of ranked voting is that it is anyone's guess how frequent a given rank order of candidates would be, or who exactly gets the first rank votes. Those will tend to be far more scattered than OTL; there is no need to consolidate your vote on a broad consensus candidate until more detailed matches to one or another political viewpoint are eliminated.
Let's say instead of 1952 that this same ranked voting system is first introduced 40 years later, in 1992. People perhaps do not realize how dramatically split the votes were in 1992. H Ross Perot actually came in second behind Clinton in the state of Maine for instance; he got a lot of popular votes, far more than Nader in the 2000 election. Also, over 142,000 voters out of just over 104 million voted for third parties not included in the top 7. Again the question of who gets on the ballot and what options voters might have to add yet others comes up, with much greater urgency than in 1952!
Just looking at the top 7, ignoring the rest by subtracting them from the national total, a candidate would require over 52 million votes to win, and assuming everyone's first rank choice is for who they voted for OTL (already a very unreasonable assumption!) the front runner Bill Clinton is 7 million short. We might crudely assume that of all the parties below Perot, 3 of the 4 would rank Bush or Perot over Clinton. Let's say the Populist and US Taxpayer's Party voters all went to Bush second, the Libertarians all went to Perot second, leaving Lenora Fulani voters to all vote for Clinton second--actually I suspect many of them would go to Perot before Clinton for reasons. This puts Clinton requiring 7 million more votes, Bush needing 13 million more, and Perot with 20 million to be apportioned among them. Whether Clinton is elected or Bush reelected, depends on who the Independents favored more on their second choice, and Libertarians on their third choice level. I honestly could not guess which would win! (my suspicion--Bush).
The idea of introducing ranked choice voting is to introduce a strongly competitive dynamic whereby voters can be very specific as to exactly what sort of President they would prefer individually, and then having sent that message their lower ranked choices would tend to converge on presumptive mainstream compromise "lesser evil" candidates. But voters might be surprised by stronger support for presumptive "third party" candidates which catapults them into contention for victory.
I think it would be very hard to game with OTL data, because the nature of our current electoral system for all offices is to put sharp limits on the viability of many types of candidate who would become more competitive in an ATL system, and to increase turnout generally since votes tend to be somewhat to overwhelmingly more effective. The type of government policies that emerge would differ and bring a cascade of ATL changes versus OTL that leaves the whole landscape completely altered.
Having this option in individual district Congress races (and state legislatures, county commissions and so forth) will similarly jazz things up versus OTL. I hasten to add I still strongly prefer PR instead, because PR addresses a great many evils a ranked choice vote for winner take all in a district does not address. The ill effects of gerrymandering for instance can be neutralized by PR aggregated across the entire region to be governed, but ranked choice voting does nothing against gerrymandering.
essentially, maybe slightly tilted to Al Gore.