One way of getting money for space travel and colonization is to form one-issue parties focused only on such funding and get them elected into national parliaments. The election campaign should focus part on the necessity of space colonization and part on the inability of politics to solve problems adequately due to its "ivory tower" character far from where the problems really are (the latter should explain the anti-congestion argument publicly and satirize politics, since support from anti-politic malcontents may be valuable). Absolute majority is not necessary, just creating a situation where no party/coalition of parties has any majority is enough, since our one-issue space party then can promise to (in parliamentary democracies, not the united states) to vote for the government/prime minister candidate supporting the most specific space funding. If no party accepts to fund space specifically, there may still be legal ways to make them relent. Try to even out the votes to make governance impossible, or if a debacle happens that gives one party/coalition a majority, try to cooperate with the opposition to vote it down. If that does not work, there is always the possibility to slow the politics down by calling for votations about lots of silly law propositions, until some parties relent and accept to fund space, then cooperate with them. Never care for other political issues, but be very clear that the space party is neither right nor left because all overpopulation-shaped Earth politics is contemptible, and that space colonization is the only solution.