The Clinton campaign has a rule for fundraisers too, spokesman Blake Zeff said: "If they're not at a private home, and if they have over 1,000 people, then they are opened."
That can be frustrating for reporters, who know something big is going on and tend to get suspicious if they're not allowed to see. So what is going on in those thousand-dollar coffee klatches, and why can't the media at least sneak a crumpet?
One reason is the candidates may be off the script, Orange County Democratic Party Chairman Frank Barbaro said.
"The real reason behind it is when somebody's giving 2,300 bucks, when somebody's writing that size of a check, they like to feel like an insider," he said. "They like to feel like they're hearing things that are not the standard stump speech, not the speech they're going to hear in a town hall in Des Moines, Iowa."
In other words, candidates are a little freer to give off-the-cuff answers, criticize other candidates or talk about strategy.
And might some of those answers be things candidates would rather not see in print?
Yes, they might, said Adam Probolsky, a GOP pollster in Orange County.
"At a fundraiser, you're there to rally the troops and make them feel good about giving money," he said. "It's a very different speech you give at that fundraiser…. A reporter asks you a question about your ex-wife, [and] you can duck and dive and go onto the next question."
Buchanan insisted McCain doesn't say things privately that he wouldn't say in front of the press, and indeed his reputation is as a "straight talker."
But then why bar the media and leave them to speculate? Observers on both sides of the aisle decried the suggestion that candidates would make promises or deals with the people who are paying for their very expensive campaigns.