Bullshit! Harris was a viable alternative. She showed it when she beat trumps ass in that debate. The simple reality here is that 84 percent of the Trump votes were from whites who voted for a man who ran the most racist campaign in history. Whites voted for racism, they voted for whiteness. This claim that the Democrats didn't offer a viable candidate is another example of the plausible deniability used to cover for the racism a lot of whites still have.
There was no corruption during Biden and Harris had no record of corruption. So again, your claim is false based on these facts. Last, third parties are out there, their candidates don't get votes because they are worthless. Where is Jill Stein now? She is sitting her ass doing nothing, but she will show up in 4 years thinking people will make her president. And the Libertarians are insane. So then if third parties want to be viable find candidates the people can support.