You're assuming both sides have equal opportunity to cheat. Democrats' base is composed largely of minorities who are easier to disenfranchise. Republicans' base is largely middle class white people.
Sure, if Democrats could prevent middle class whites as a group from voting, they would; they can't. Replublicans absolutely can price poorer black people out of voting.
Democrats' base is also composed of a huge population of over ten million illegal immigrants. They are often well-integrated with Democrat-aligned political organizations, and many have family or friend connections to citizens who can vote legally. And given the political climate, it's obvious they massively favor Democrats.
They don't have to do anything as complex as voting at several polling places. They just have to go vote once. That's easy to justify to yourself.
How exactly are they registering to vote? Have you ever actually talked to, or worked with, someone in this country without a visa? I have and without exception they stay as far from official government interactions as they possibly can. They don’t fly, they mostly don’t have health care, they don’t get welfare, food stamps, disability or any other kind of government assistance — all they do is work and eat and pay rent. In many ways they are the ideal Republican fantasy!
They definitely do not vote! There are more published examples of Republican politicians illegally voting than there are of illegal immigrants voting.
Um, that may be true in you local experience, but statistically it is really, really false.
There are lots of places where illegal immigrants can receive drivers' licenses and other forms of government assistance. And they do. For example, just in California, there are now a million illegal immigrants with driver's licenses. [1]
"Through June 2017, the Department of Motor Vehicles has issued approximately 905,000 driver’s licenses under Assembly Bill 60, the law requiring applicants to prove only their identity and California residency, rather than their legal presence in the state."
In California, a driver's license is enough to vote. In fact, it automatically registers someone to vote.
Sure, if Democrats could prevent middle class whites as a group from voting, they would; they can't. Replublicans absolutely can price poorer black people out of voting.