Yes, even infants. Obviously, the legal parent or guardian of the child would have the right to help the child in the voting process until the child is capable of do so without such aid. Still, many of the decisions that are made today directly affect the future of our children, yet those children have no voice in those decisions. Because they do not have the ability to vote, politicians largely disregard policies that would directly benefit children, and instead focus on helping those in a significantly aging population.
Who better to vote on issues of school bonds, social security, the environment, foster care systems, the deficit, etc. than those citizens who are either directly impacted or who will have to foot the bill? Sure, government officials claim to be acting in the best interests of children, but without having to court their votes, all that is given is lip service.
To those who claim that children are not ready for this responsibility, that they will be too easily manipulated by people who do not have their best interests at heart, or that they will simply vote the way they are told by their superiors, I would like to remind you that the same arguments were given when newly freed slaves, and later women, were wanting their voices to be heard. I will also add that all of those arguments are true for any human being. I know of many adults who are not informed enough to vote, as well as many adolescents who nearly have the capability to run a country (as many children have done throughout the history of the world).
Every citizen deserves the right to help shape the course of our nation. This is a democratic republic. It works best when all of our voices can be heard.