That is why some of the Census Bureau's methods would work well for an election. But the goal of an election is very different from the goal of the census. One seeks an accurate count of the choices made by some Americans called voters. The other seeks an accurate portrait of all Americans themselves. That is why sampling, the use of modern statistical methods, essential for an accurate census count, didn't work so well in predicting the choices of actual voters.
Voters are by far a messier lot than citizens in general, hard to pinpoint before election day.
Voters are not selected by anyone, nor do they qualify to vote by any income characteristic or any demographic other than age. Before and after voting day, they can and often do refuse to answer questions about their preferences, change their minds or provide misleading responses. They are self-selected. If they don't turn out, that's that. The government doesn't go after the sick, the unaware, the uninterested or the hostile to demand that they make a choice among the candidates.