Get them to vote before their brainwashing in the government-run schools begins to wear off.
I think you hit on the right reason, before they realize and find out that socialism sucks big time. Of course this does not imply that republicans have the perfect answer either. But as it stands now they are the lesser of the two evils.
Government itself is a lesser but necessary evil. But when people start thinking government is their salvation, it quickly turns into a greater tyrannical one. “The price of freedom is eternal vigilance”—no way can you hear that being taught in today’s public schools.