In the California Green Party, when a motion is about to be voted on, the facilitator asks if there are any blocking concerns. If there are none, the motion passes, no vote needed.
If there are blocking concerns, then it goes to a vote. If it's a policy matter, it must pass by 80%. So, in effect, one person can block a policy vote from passing, as an 80% vote can seldom be mustered.
Much of my probing into the Green consensus process started due to an ongoing bruising war within the California GP, which I, as co-chair of the Green Party of L.A. County, am directly involved in.
Over two years ago, Mike Feinstein, co-founder of the California GP and current City of Santa Monica council member, took a $10,000 check made out to Green Party of L.A. County and deposited it into a personal bank account. This is not conjecture; we have a public statement from the major donor and a copy of the cancelled check with Feinstein's endorsing signature on it.
After following the lead of the State GP on this, and seeing them do nothing about this for months and months, I finally started researching it on my own and discovered that, in my opinion, they were inept at best, and then filed criminal and civil complaints against Feinstein. (I have gotten much support for this while others, of course, want my head on a platter - so much for Green values of openness, transparency, and accountability, eh?).
I'm convinced that the consensus-based, we must all be on the same page and happy about it, style of decision making in the State GP is one of the main reasons for the inaction. Were the Reps or Dems to face something like this, they'd either bury it so deep no one would find it, or take the miscreant out front and have him publicly shot. What they would not do is dither endlessly about it for months.
PS Feinstein no longer holds any post in the GP. In a recent unintentionally comic Op-Ed, the Santa Monica Mirror, who has never run an article about this, said the GP had conducted a "Stalinist purge" of Feinstein. Damn, and here I thought it was my pals in ANSWER who were the Stalinists...
Links to newspaper stories about this ongoing psychodrama http://www.polizeros.com/categories/greenParty/2003/05/01.html#a1906