Entities mentioned:
- Joe Biden: Legacy, Duty, Power
- Anita Dunn: Loyalty, Professional pride, Duty
- House Oversight Committee: Righteousness, Control, Influence
- Robert Hur: Duty, Justice, Professional pride
- Bruce Reed: Loyalty, Duty, Professional pride
- Steve Ricchetti: Loyalty, Duty, Professional pride
- Mike Donilon: Loyalty, Duty, Professional pride
- Dr. Kevin O'Connor: Professional pride, Self-preservation, Duty
- Anthony Bernal: Self-preservation, Loyalty, Duty
- Annie Tomasini: Self-preservation, Loyalty, Duty

Article Assessment:
Credibility Score: 70/100
Bias Rating: 55/100 (Center)
Sentiment Score: 45/100
Authoritarianism Risk: 30/100 (Generally Democratic)

Bias Analysis:
The article presents multiple perspectives, including both supportive statements from Biden's former aides and the ongoing Republican investigation. While it leans slightly towards defending Biden, it also includes potentially damaging information, maintaining a relatively balanced approach.

Key metric: Presidential Approval Rating

As a social scientist, I analyze that this article highlights the ongoing debate about President Biden's cognitive abilities and its potential impact on public perception. The testimony of former aides, particularly Anita Dunn, appears to be an attempt to counter narratives about Biden's mental fitness. The Republican-led probe and the refusal of some aides to testify suggest a politically charged atmosphere. This investigation and the associated media coverage could significantly influence public opinion on Biden's capability to lead, potentially affecting his approval ratings and re-election prospects. The emphasis on aging and cognitive abilities in high office also raises broader questions about age and leadership in American politics.