That's not true, there are a few democrats caught comitting voter fraud. Although it's people who only tried to vote once and the "fraud" was because of paperwork issues like their change in voter registration not going through in time.

Meanwhile republicans go out of their way to vote multiple times or illegally on behalf of others. They even do it as an attempt to "prove" that democrats do it, sometimes referred to as trying to frame someone for a crime.

TL;DR: It's only conservatives who intentionally commit voter fraud.