This is actually a fairly flawed question. Abu Bakr had the full support of most of the early Muslim to the point that any contention to his rule was disregarded. Further, it wasn't Ali ibn Talib who was the most likely to take a piece of the government or rule; it was Abu Sufyan, the former ruler of Makkah and close relative of Muhammad and the one who had the most claims to royalty in terms of Arab tribal tradition. In terms of who Muhammad would name, it would be Abu Bakr, he was the closest to Muhammad and had been with him the longest, Ali was a youngster and in no position to take the reigns of leadership, nor would he want the role considering the position Abu Bakr inherited.
The so called Sunni-Shi'i split has only a small amount of influence from the fact Abu Bakr was chosen instead of Ali ibn Talib. It is only the major criteria for Zayydi Shi'i who comprise the moderate Shi'i community. When you look at the history and critically read it, it is perhaps clear, that Shi'ism was the reaction by formerly non muslim communities to the new Calipahte, especially in Kufa, southern Iraq and Northern Iran which became the powerbases of the Shi'i movement and then later in Northern Africa in places like southern Tunisia. Shi'i believes only became an actual proto movement during the reign of Uthman ibn Affan when the preacher Abdullah ibn Saba al-Himyari arrived in Makkah and began preaching that Ali was Allah. This sort of mantra was the common epithet of the early Shi'i who would later be called the Ghulat or the exaggerators.
So, there would still be a Shi'i like religion regardless of the successor in Islam, Ali was just the excuse for the new series of religious beliefs which birthed Shi'i. You can clearly see this by reading the works of Shi'i scholars, who rarely speak on the transfer of power but on how Ali was the prophet and that Ali was deputy of Allah or that the family of Ali is the foundation of the earth and those within are infallibles with godlike powers walking on water and such. Islam is doomed to not be united in actuality, it is impossible to organically create a movement like Islam across vast lands within two decades and expect there to not be cracks. Islam also already had two break away groups before Shi'i Islam and the arrival of Abdullah ibn Saba al-Himyari; in the Murji'ah and Khawarij movements, the latter which existed while Muhammad was alive. These two groups also defined early Islam much more so perhaps than the Shi'i, the Khawarij for instance led directly and indirectly to the fall of the Abbasid and Umayyad caliphates and assassinated numerous figures, including Ali ibn Talib. Curious too, when you look at the early Shi'i who are supposed to be the defenders of the family of Muhammad, but then ally and fight actively with the Khawarij against the Umayyads despite the Khawarij killing Ali ibn Talib, it shows readers clearly, that the Shi'i much like the Khawarij where a religious group that began not due to Ali, but as a rebellion and resistance to the Umayyad caliphate and specifically an animosity between Iraqis and Syrians.