Caught on video: The moment Hillary Clinton collapses as she is helped into her van after being rushed from 9/11 memorial - but her aides try to explain it away as 'overheating'
- Democratic presidential candidate was abruptly led away from service at around 9:30am on Sunday
- Video footage shows her appearing to lose her balance on the sidewalk before getting helped into a car
- The clip shows her knees appearing to buckle on the curb before her aides rush to her side to help
- Nick Merrill, her traveling press secretary, said Clinton 'overheated' as she was taken to Chelsea's home
- Despite the concerning video, she emerged a short time later and said: 'I'm feeling great'
- Temperature was around 80 degrees at Ground Zero during the service
- The latest incident will raise further questions about her health that have been pushed by opponents
- Last week she refused to answer questions by DailyMail.com about a concussion she suffered in 2012