First, note that the Constitution's Supremacy Clause, Clause 2 of Article VI, means that only those federal laws which are reasonably based on the limited powers which the states have expressly delegated to Congress via the Constitution take precedence over state laws.
And with respect to constitutonally delegated power for the feds to regulate voting, the states have granted Congress the specific powers only to protect such privileges on the basis of race, sex, tax status, and age as evidenced by the 15th, 19th, 24th and 26th Amendments respectively.
Regarding the so-called right for non-citizens to vote, the Supreme Court clarified in Minor v. Happersett that citizenship does not automatically confer the right to vote.
However, the problem with state officials fighting federal power grabs, such as with this voting rights issue, is the following. I'd be willing to bet money, because I'd probably win most of the time, that state officials, including state lawmakers, are low-information citizens who don't know how to argue issues like this voting rights issue.
Finally, remember that the reason that DC policy-makers have been using the Supremacy Clause to successfully usurp state powers is the following imo. Federal bureaucrats have been taking advantage of the fact that multitudes of low-information voters don't understand that the feds don't have the constitutional authority to do most of the things that they are doing these days. This is because generations of parents have not been making sure that their children are being taught the federal government's constitutinally limited powers, particularly the 18 clause of Section 8 of Article I, as the Founding States had intended for those powers to be understood.
In fact, Judge Andrew Napolitano will read Section 8 to you in three minutes.
Judge Napolitano & the Constitution
“I’d be willing to bet money, because I’d probably win most of the time, that state officials, including state lawmakers, are low-information citizens who don’t know how to argue issues like this voting rights issue.”
I worked in Kansas a few years ago, before Kobach was elected to office, and followed him a bit through radio and papers. He is not a low information citizen/official.