It’s controversial because one party favors strong voter ID laws which means in the American system the other party must oppose it. A more concrete answer is that the party that favors less restrictions on voting, believes that everyone under the governed regardless of disposition, nationality, age, etc. should have the right to vote. The other party believes that the law says you must be 18 and a citizen to vote in federal elections, and that’s how it should be, and if the law says that then there must be someway to verify that.
That other party has a long history or preventing "the wrong people" from voting by any means available: murder, intimidation, "literacy tests," gerrymandering districts, and making requirements that are very difficult for the "wrong people" to obtain. The level of hysteria over election fraud is wildly disproportional to the number of documented cases of said fraud.
We really ought to bring back literacy tests. They should just be applied to all voters.. Even better, you can't vote unless you can pass a US Citizenship Exam. Then we could open the voting up to all citizens regardless of age, too. Win, win, win.
