The Virginia gubernatorial debate being held on October 24 is jointly sponsored by WDBJ7, and the Virginia Polytechnic Institute & State University (known as Virginia Tech).
WDBJ7 is sending an automated response to people who advocate that the debate include Rob Sarvis. It says, “Thank you for your interest in the debate. The guidelines for the debate were negotiated by the two major party candidates. WDBJ7 originally recommended that the door be opened and a reasonable threshold be set for Mr. Sarvis to participate. I believe no other debate organizers had even given him that opportunity. The particulars of the language were negotiated by the major party candidates. Once the agreements were signed, WDBJ7 was bound by the rules or risked losing the opportunity for the voters of Virginia to hear any of the office seekers debate the issues.”
SDBJ7 has a story on Sarvis’ reaction to being excluded from the only remaining debate.
The webpage of Virginia Tech does not appear to discuss the October 2013 debate. Virginia Tech has hosted general election debates in the past, including the US Senate debate of 2012, in which only the two major parties appeared on the ballot.
UPDATE: here is an account of the major party gubernatorial debate held October 10.