Rangel is one of the most senior Democrats in the House; he chairs the Ways & Means committee.
And he's a slimy crook.
Pelosi won't ask him to step aside - even though she and Harry Reid PROMISED us the most ethical Congress ever.
Therefore, Obama MUST.
Obama is the chief of the party, now.
If he fails to ask Rangel to step aside, then he's admitting he's a slimy crook, too.