The Dems are now a hard-Left party. For a leftist, the end justifies the means. If you have to cheat to win, then you cheat. And so they cheat. Case in point: Arizona election fraud. See here, here, and here.
When caught, leftists lie about their cheating and about their lying. Do leftists ever tell the truth? Yes, of course — when it serves their purpose. Truth is not a leftist value. Their highest value is power, its gaining and maintaining.