I cant imagine a voter cant have standing. If a citizen can vote and especially if they are natural born, it sure does have impact on them whether an illegitimate person is running for president.
In principle I’d agree with you, but I’d wager that the courts would rule a voter has no standing. Someone with a direct interest e.g. someone else on the ballot may, not sure which court would want to hear the case. IANAL, just an experienced guess.