please look up the event of Hazrats Fatimas house being besieged....

Al-Bukhari narrated:

Umar said: "And no doubt after the death of the Prophet we were
informed that the Ansar disagreed with us and gathered in the shed of
Bani Sa'da. 'Ali and Zubair and whoever was with them, opposed us,
while the emigrants gathered with Abu Bakr."-Sunni Reference: Sahih al-Bukhari, Arabic-English, v8, Tradition #817 shows Imam Ali had supporters in the political sense... i.e SHIA of Imam Ali