Voting Yourself Money
In the comments, Robert raises a favorite conservative suggestion: take the vote away from anyone whose income comes from the government. And he's consistent enough to argue that this includes not just welfare recipients and retirees on Social Security, but also teachers, police, and military personnel (and later, he properly extends it to employees and stockholders of companies with government contracts)*. The idea here is that recipients of government money have a selfish incentive to vote themselves more money. Taking the franchise away would correct that distortion.
Robert's suggestion makes sense only if you conceptualize government spending as charity. The important point about charity is that, while it may be morally right to give charity, the recipient cannot claim charity. Scrooge may not be a very nice person, but he wasn't violating Tiny Tim's rights under the charity model.
However, the plausibility of conceptualizing all government spending as charity collapses when you consider that we're talking not just about welfare recipients, but also fundamental services like teachers, soldiers, and police. Hiring police is not an act of charity toward the officers, it's a moral imperative for the maintenance of society. So we can all agree that there's some level of spending that's morally required (of course, some of us would argue that the moral benchmark is set much higher and includes some degree of welfare)**.
But once we agree that there's some morally required level of spending, a symmetry appears between the recipients and the payers, between the disenfranchised government employees and the mostly-still-enfranchised taxpayers. Those taxpayers have a selfish incentive to cut spending, meaning that leaving spending decisions only in their hands will lead to lowballing the amount of spending -- which will be a distortion so long as, as we've agreed, the morally mandatory level of spending is greater than zero. Thus taxpayers are just as able to "vote themselves money" through supporting lower taxes as welfare recipients are to vote themselves money through increased taxes.
*It's interesting to note how this conflicts with another old conservative favorite, also mentioned in the comments, of allowing only military personnel and veterans (and people who do alternative service) to vote. Comparing those two suggestions to the popular liberal ideas of Instant Runoff Voting and strengthening unions, it becomes clear which side sees democracy as a moral imperative to be expanded, and which sees the franchise as a privilege to be given or withdrawn in the service of other ends.
**And if the morally required level is zero, then why not skip the awkward hack of taking away the franchise, and skip straight to direct abolition of taxation, relying on private sector charities to distribute any largesse the rich may feel like giving?