A republic tries to safeguard the minority, hence the US system with its safety checks such as the electoral college.
I heard that is what the Democrats want to remove for mob (democratic majority) rule. That could be hearsay.
Also, only citizens should vote and vote once.
That is what you are told in school. That is never how it works accept in small, homogenous and established communities, and even then it devolves into fascism.
If the safety measures of a republic are removed, then there will not be a republic anymore but a socialist authoritarian state, which for the US would likely be in the form of fascism where the government controls private enterprise through threat of force.