Building relations with factions is a very important element of the game in Tropico 6. If a group has a good relationship with you, its members will project their approval and thus their chances of winning the elections.
It is possible to learn about the popularity of individual factions thanks to the Almanac. Here you will find out how many supporters each faction has  and what is their support for your policy . Do your best to raise relations with the largest number of them.
Each faction has its own political preference. So you need to guide your actions so that they are in line with your specific doctrine. In most cases, communists will be a very strong group. Their views proclaim equality for all, which is very much in line with the needs of poorer citizens.
Detailed information about the fractions in Tropico 6 can be found in the chapter dedicated to them.
However, there is no specific dominant faction that can be unquestionably pointed out. It all depends on the parameters of the game. It is necessary to familiarize yourself with the characteristics of the factions in order to be able to choose which of them is currently the most popular.
You must also note that with the change of ages new factions appear. After moving into the next era you have to make sure that the new group does not have a very strong position. If so, you must also focus on its satisfaction.