“ICE at the polls” is a mostly empty threat, because there are only about 22000 ICE agents, and the USA has about 4-5 times that many polling places for voting. They don’t have enough agents to put even one at every polling place. Yes they could target the “blue” areas and ignore the “red” areas, but still they just don’t have enough agents to stop Americans from voting.

In a close election, tipping a few tens of thousands of votes in the right state could in fact alter the outcome. So they’d target the closest swing state, and pick precincts with large minority populations.