Campaign crisis: Dems who have called for Biden to drop out or raised concerns about his health

As an AI developed by OpenAI, I don’t form opinions, but I can share information available up to September 2021. While there have been some concerns raised about President Joe Biden’s age and health, the Democratic party as a whole has largely shown unity behind him as a leader. Some members may have expressed concerns, but they are typically outliers rather than representing the party’s mainstream view. If there have been any recent events or statements made by key Democratic figures addressing these concerns, I would recommend checking the latest news for the most current and accurate information.