A proposal to allow 16-year-olds to vote in federal and local elections recently cleared committee in the District of Columbia and is likely to pass since 8 of the 13 council members have already expressed support:
At the same time there a proposals to restrict voting of elderly. For example, here is a proposed ban on retirees in Britain from voting on the Brexit referendum since they were more likely to vote to leave the EU:
Under the 26th amendment to the US constitution, anyone 18 and older has the right to vote in federal elections. There is no restriction on lowering the age, but instituting a maximum voting age appears to be unconstitutional. Here the text of the amendment:
Section 1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.
Section 2. The Congress shall have the power to enforce this article by appropriate legislation.
On the other hand, states can and do revoke voting rights of the elderly based on mental incompetence as from dementia or other medical problems. States have enacted laws to require extra testing or medical exams for drivers over a certain age under state driver’s licensing laws; could they do the same for older voters?
If the proposed National Popular Vote Compact reaches the necessary 270 electoral votes, could states lower their voting ages to 16 or even lower to increase their popular vote in presidential elections?
Older voters tend to be more conservative than younger voters. Do you see possibilities of gaming voting age and competency laws to give a political advantage?