What was the main reason that immigrants in cities became new voters in large numbers?

The first reference would be “When thou passeth through the waters I will be with thee, and through the Rivers, they shall not overflow thee,” Isaiah, 43:2. This is a verse she alludes to when they cut some dry trees, to make rafts to carry them over the river: and soon her turn came to go over: By the advantage of some brush which they had laid upon the raft to sit upon, she did not wet her foot (which many of themselves at the other end were mid-leg deep) which cannot but be acknowledged as a favor of God to her weakened body, it being a very cold time. “When thou passeth through the waters I will be with thee, and through the Rivers, they shall not overflow thee,” Isaiah, 43:2. On Saturday they boiled an old horse’s leg which they had got, and so we drank of the broth, as soon as they thought it was ready, and when it was almost gone, they filled it up again. 
Second Bible reference is, Psalm 137:1, “By the rivers of Babylon, there we sat down: yea, we wept when we remembered Zion.” 
This is about a month after she had been captured, she was starving, they were still traveling.

Immigrants were supported by political machines. On the off chance that you offer the free lease, nourishment, lodging and medicinal, foreigners get used to getting it and would prefer not to lose it so they vote in favor of the gathering that will continue giving it to them. 

Immigrants who need to live here and be gainful know the main path is to get included with their groups and be positive. The American Way likewise incorporates being a group, assisting with positive change and locally, territorially and governmentally, that implies turning into a US Voter. You get your entitlement to vote by turning into a resident. Accordingly, turning into a NEW subject is the best approach to get the vote, not remaining a migrant.