Traditionally there are broadly-accepted qualifications for the nominal right to vote set out in the Fourteenth , Nineteenth, and Twenty-Sixth Amendments to the Constitution. These are summarized by "US citizen, not a felon, and at least 18 years old."
There are occasionally explicit efforts to change these qualifications. For example, xenophobes are trying to decrease legal immigration and block citizenship (& voting rights) for the children of illegal immigrants. (This is part of a broader effort by the current Administration to restrict legal rights for racial minorities. Compare recent efforts to deny passports to US citizens and to deport US veterans.
Meanwhile liberals are trying to enfranchise ever-larger populations. Changing such standards at the federal level could potentially effect millions of people. Significant changes could be made at the state level as well, and there are variations across states.
Both the proposals on the left and right are most likely to affect racial minorities, and align with favoring their own demographics.
Links to other posts in my voting series are below the picture.
