For the first time in U.S. history, the Presidential election of 1860 featured four major party candidates. There has not been a similar one since then. But the U.S. election of 2020 might change all that.
Looking first at the 1860 election, it was of course the one that presaged the Civil War. The principal reasons that led to the eventual secession of the Southern states from the Union were front and center in that election. They were:
The maintenance of the institution of slavery in the states that had it. (In fact, no candidate held the position that slavery should be abolished in any of the slave states, but the latter made it an issue anyway.)
The matter of the expansion of slavery further into the Western Territories than it had already gone. Many from the non-slave Northern states wanted that practice to end, completely. The Northern Democrats (until that time, the Democratic Party had been THE party of slavery) were led by Sen. Stephen A. Douglas of Illinois (he of the famous "Lincoln-Douglas debates" of 1858). They held that slavery could be allowed to further expand into the territories, if the residents of each voted in favor of allowing the practice. This doctrine was called "Popular Sovereignty." A major issue for the slave-holding states was the allowance of the virtually unlimited expansion of slavery into the Territories.
The question of protective tariffs, favored by the Northern states to protect the growing industrial sector, opposed by the Southern states.
The matter of the Federal government's role in the expansion of the nation westward, in addition to the matter of the expansion westward of slavery. Non-pro-slavery Northerners were generally in favor of an active role of the Federal government in the expansion of the economy, at the time particularly focused on Federal support for building a trans-continental railroad and for providing free land in Federal territories for "Homesteaders" (which of course would be contrary to the Southern interest in establishing slavery in the same).
Absolute abolition of slavery was the goal of the Northern Abolitionist Movement, of course, but none of the eventual four candidates, nor their parties, took that position. That did not stop the Southerners from spreading the myth that the Republican candidate, Abraham Lincoln, was secretly in favor of abolition (which at that time, having been both a white supremacist and in favor of "back-to-Africa" as a partial solution to the slavery problem, he was definitely not).
There were several other major issues which did not figure in the election, but definitely did figure in the post-Civil War politics that have been curse of this country down to the present day, and have led me to the conclusion that in fact, in terms of the outcomes of every issue other than that of chattel slavery, the South did win the Civil War. E.g., the spread of the Dogma of White Supremacy over the whole country; the development of an Imperialist foreign policy that had only just begun with the fighting of the Mexican War, led by Southerners; and the maintenance of the "Doctrine of States Rights," primarily to protect the states' right to discriminate against designated sectors of the population, like African-Americans and women, and more lately the LGBT community. (An odd footnote to that one is the fact that the pre-Civil War President James Buchanan, whose policies did so much to bring the regional conflicts to a head, was actually the first, and so far only, gay President the U.S. has had.)
In the end, there were four candidates for the Presidency. The brand-new Republican Party, made up of the "Northern Whigs" nominated the moderate Abraham Lincoln. It was opposed to the expansion of slavery to the territories and supported the pro-industrial- expansion policies of the Whigs. It also included the Temperance Movement and elements of the anti-immigrant "American Party" (the "Know-Nothings"), both of which have played major roles in Republican policies in the ensuing decades --- see Prohibition and the 1924 Immigration Act --- right down to the present --- see the current anti-immigrant policies and the "Drug War." The Democrats split, with the Northern Democrats nominating Sen. Stephen "Popular Sovereignty" Douglas." The Southern Democrats nominated the pro-slavery, then-sitting Vice-President John C. Breckinridge, while the Constitutional Union Party, formed from Southern Whigs and others, adopted a platform which avoided the question of slavery altogether. Their nominee was John Bell.
Lincoln won with just 39.8% of the popular vote, but 180 electoral votes, a majority of the 152 then required. A big difference between 1860 and 2016 in terms of the meaning of the popular/electoral vote differentiation was that the next-highest popular vote total was garnered by Stephen Douglas, with 29.5%.
(A couple of historical footnotes, one minor, one not. (1) In the 1850s, Vice-President Breckinridge had had a mining town in Colorado named for him. When he joined the Confederacy for the Civil War, becoming a General in the process, the town, pro-union, changed the spelling of its name to Breckenridge. (2) A candidate for the Northern Democratic nomination in 1860 was a Senator from the slave state of Tennessee [which chose to join the CSA] named Andrew Johnson. When going into the election of 1864 President Lincoln wanted to "broaden his appeal," he dropped the reliably pro-Northern Hannibal Hamlin and chose Johnson, who had been a pro-Union but otherwise Southern Democrat whom Lincoln had appointed as Military Governor of Tennessee after most of it had been re-taken by the Union Army, as his Vice-President. As President, it was Johnson, of course, who laid the groundwork for the eventual destruction of Reconstruction. Think of how, leading up to the election of 1944, FDR dropped his progressive Vice-President Henry Wallace for Harry Truman, and how nuclear-use and post-war policies might have been very different had he not done so.)
And so, very briefly here, let's look at the possibilities for 2020. (If this prediction becomes more likely to hold water than it might be considered to do so now, I will of course be returning to this subject.) First, I do think even moreso than I did when subject, that when things get just too hot (and they are getting ever-hotter), pardoning everybody in his entourage, including himself, Trump will resign the Presidency. He will then proceed to set up an openly fascist party (although he won't use the word in its name). His chief-of-staff will be Steve Bannon, and he will bring in also Corey Lewandowsky, Roger Stone, his family members, Kelly Anne Conway, and so forth. To begin with, he will be funded by Koch and Mercer money.
The Republican Party will of course stay in business. As the "OMG, why did we get stuck with Trump" Republican David Brooks of The New York Times has said: "As long as [Trump] is in power the G.O.P. is a house viciously divided against itself, and cannot stand." There are a variety of "anti-Trump" so-called "liberal" Republicans who would compete for its nomination. The irony is that their basic policies are very similar to Trump's, just with the traditional Republican/let's-use-dog-whistles style and absolutely the same so-called "small government" mantra (except when it comes to such things as women's choices for their bodies and everyone's choices for their Recreational Mood-Alerting drugs), lower taxes for the wealthy, massive de-regulation (only a little less radical than Trump's), and so on and so forth.
As for the Democrats, it is becoming increasingly clear that they will split into two wings regardless of what happens to the Republicans. The split is becoming so sharp(and it should, in my view) that there may well end up being two Democratic Party candidates in 2020, just as there were in 1860. A fifth possibility is the Kasich-Hickenlooper ticket (already) being floated about. Gov. Kasich tried to put the kybosh on that very quickly (and Colorado's Gov. Hickenlooper is on the board of "New Democracy"), but of course he would do that now. It's very early.
At any rate, the election of 2020 could well see four major parties in the field as in 1860 (and perhaps five, at the beginning at least). The issues facing the country now are as momentous as they were in the years leading up to that election, and the in nuclear war/global warming arenas, much more momentous. So, we will all stay tuned.