The qualifying standards were tougher when Kerry "qualified" for his Boston Marathon in the late 1970s. There still pretty tough, according the the Boston Athletic Association site. For the 2005 Boston Marathon, male runners have to be 45 years-old to slip in with a 3:30 qualifying time. And Kerry, as I mentioned in a previous post, turned 35 in 1979. (And if you believe his biography, he was working 25 hour days in the DA's office while also training for marathons in the late '70s.)
Not so. See my post #6. You just had to show that you could run the marathon in less than four hours. As the Marathons get bigger, more restrictive qualifying standards are developed. The organizers try to restrict the numbers for a variety of reasons, particularly logistical. Even the Marine Corps Marathon in DC is done through a lottery system.