This is fun:
Support mass immigration of people from other countries who are likely to vote democratic. Basically highly educated people and POC, and make it easier for them to become citizens to vote so they can drown out MAGA. An extra 10-20 million US voters from Europe, Canada, Australia, Japan, etc who are likely to vote Democratic will drown out MAGA in elections.
Encourage mass movement of democrats out of safe states, and have them move to swing states and swing districts (as mentioned by OP). 200k democrats leaving safe blue or safe red states and moving to swing states and swing districts will swing close elections for the house, senate and presidency.
Encourage large scale voter suppression and voter ID laws in white rural areas (again, mentioned by OP).
OP mentioned infiltrating MAGA, but they should infiltrate MAGA to promote divisions. Democrats should infiltrate MAGA talking about how catholics aren’t real christians. or how latinos and asians will never be white. Or how women will always be inferior. create divisions in MAGA between men and women, between protestants and other christians, between whites and light skinned POC.
Mass rebuilding of the labor movement. High school educated whites have left the democratic party. However high school educated whites who are in labor unions are far more likely to vote democratic vs high school educated whites who are not in labor unions. Mass unionization of high school whites in manufacturing, service work, etc.
Promote propaganda showing Trump being in favor of POC, muslims, feminists to weaken his base.
Ridicule MAGA men for being so spineless and cowardly that they need a child molester to protect them from brown people because they are terrified of brown people, and because they know they’re so incompetent that they can’t survive in an equal society where they have to compete against immigrants who can’t speak english. MAGA are highly driven by concepts of courage, bravery, strength and masculinity; so undermining that would hurt their movement.
Mass support of third parties that split the GOP vote. Libertarians and other 3rd parties.
Give homeless people money to move to swing states and swing districts and vote democratic in elections.
At root the question is how can we increase democratic voters, reduce republican voters, and make sure that this especially applies to swing states and swing districts. Theres a lot of tactics to try to do this.