Plus, the Third and Fourth Republics were essentially parliamentary republics. It wasn’t until the Fifth Republic that there was a strong President, and even then there are some elements of a parliamentary system (prime minister chosen from party with majority in the Assembly).
Maybe Argentina? It’s Constitution is doctrinally based upon the US Constitution and was originally written in 1853. They have separate elections for president, congress, and choose justices as the US does.
There have been a few amendments and the Peron government may have “interrupted” the continuity in the 1950s, but it has basically remained intact since the 1850s.
You count Peron as an interruption but not the later coup and military regime?
Yea, might have helped if I just kept reading…I withdraw Argentina as a possibility
Costa Rica is definitely the Latin American country with the longest continuous history of constitutional transfers of power. Colombia is next. Venezuela’s current democracy dates to 1958, if you discount the short-lived coup against Chavez, though the current constitution is more recent.
Here’s a list of countries by current system of government. Only the countries in blue would fit the criteria in the OP.
Going through the list by region:
In the Americas, after the US, Costa Rica is the oldest presidential republic with continuous constitutional transfers of power, dating to 1948.
Aside from Switzerland, Europe consists of parliamentary republics, constitutional monarchies (I think all with parliamentary systems), and/or countries that have been under dictatorships more recently than 1948.
Most of Africa was under colonial rule up until the 1950s or later, and the few that weren’t have been dictatorships at some point.
All presidential republics in Asia have been dictatorships as some point since 1948.
Oceania has no full presidential republics, and the ones with a mixed system were colonies until after 1948.
So if Mexico and Switzerland are rejected, the answer is Costa Rica.
I’m still vacillating on Mexico. You can have an authoritarian republic, even if it’s not very democratic, and if they followed their constitutional norms during that period, I suppose it may qualify.
What’s a few coups and juntas between friends, anyway? 
More seriously, they were under a military government as recently as the early 80’s (eg during the Falklands War) so I think they’re excluded.
Hmmm…
Venice - up until Napoleon conquered it in 1797? The Doge IIRC was elected (for life).
The Vatican? The pope is elected, by a limited franchise. IIRC, about half the electors tended to reside in the Vatican.
You are correct, sir. I now recall that(and read it again today), but it fell out of the ol’ noggin for lack of use.
ignorance fought, or memory jogged…either way.
The Mexican government between 1929 and 2000 operated more like Richard J. Daley’s Chicago or Huey Long’s Louisiana than the Stalinist USSR. There was a deeply corrupt political machine that controlled everything, but there was some effort to keep their political base happy.
The OP isn’t asking for the oldest democracy or presidential system that ever existed, but the present one that has the longest continuous existence.
I can’t see how this qualifies as a presidential/legislative system either. I think you need to read the OP with a bit more care (or maybe just the thread title ;).
I am extremely pro-Chavez, but even I’d acknowledge he wasn’t a liberal democrat, at least after the first few years. (I’m not really a democrat either, so the fact that he and Maduro have been increasingly soft-authoritarian doesn’t bother me). Chavez won a series of fair elections, and he pretty clearly had majority popular support in every one, and Maduro (barely) won a competitive election last year as well. However, I don’t think for a minute either of them would have stepped down if they had lost. Henry Rangel said, pretty much, that he would stage a coup if Chavez lost the 2012 election, and he was promoted to commander-in-chief of the armed forces shortly afterwards, so I think we can assume Chavez approved of that remark.
Colombia’s government tacitly supported right wing death squads in the 1980s that killed a large percentage of the far-left party’s candidates (the former guerilla group that decided to lay down the arms, I forget the name), so I’d hesitate to call them much of a liberal democracy during that era.
Well, considering the majority of the regimes we would call “democratic” were European, and most over Europe was overrun in WWII, there’s not a lot to choose from.
What are the European exceptions to WWII occupation - Spain and Portugal are out; both had military dictatorships until recently. Sweden and Britain, monarchies with parliaments. Finland - Parliament? Turkey, also parliament.
How does Iceland measure up? I believe it’s more of a parliamentary democracy.
the rest of the world? AFAIK, all of South America was dictatorships over recent history; Africa, ditto. South Africa - parliament? Most of Asia was colonized, or is still traditional monarchy. As the French Revolution demonstrated early on, not too many places manage to throw off the yoke of tyranny and make a go as a continuing democracy, and creating a president rather than installing the monarch as a figurehead tend to indicate a radical upset - radical upsets tend not to be stable. Countries that evolved into democracies tended to evolve into parliaments with figureheads and there’s a lot more, longer stable versions of them.
I still say the Vatican qualifies if we are looking at elected leader, legislative council. the only squirming is that it is an appointed council and perceives its mission to involve more than local administration.
Again, I am not asking about democracies generally. I am asking about a republican form of government with a presidential / congressional system. Since the Pope holds power for life or until abdication, and appoints all bishops, cardinals and officers of the Vatican, I fail to see how it is of any relevance to the inquiry.
President-for-life (or whatever title, Doge, Pope) is a much longer established concept than fixed and limited term. In fact, IIRC, there was no limit on US presidents originally - Washington chose to limit himself to two terms, and set the moral precedent. It was only when Roosevelt II chose to make himself president for life 
that the constitution was amended.
If Washington himself had been more ambitious, if the Federalists passing the Alien and Sedition acts (the original Patriot Act) had been more invested, if the 13 colonies had not all agreed to the new constitution - history would have been very different indeed.
Are there any governments meeting your criteria that predate WWII?
The Vatican doesn’t have anything remotely resembling a legislative council. Neither the College of Cardinals nor the curia have any legislative function. In fact the chief executive and the sole legislator (and the final court of appeal) are the same person, so there is no separation of powers of any kind.
The Vatican is an elective absolute monarchy.
Yes, history would be different if a lot of things had been different. However, I am not asking about a Henry Turtledove novel, but actual events.
I suggest you read the thread start to finish to follow the discussion.
See my post #25. If you’re not going to read the thread, there’s not much point in posting.
Again, read the OP. You’re answering a question that hasn’t been asked.
And anyway France only once had a presidential system, that lasted just long enough to elect Napoleon the lesser to the presidency.