"You might not find as much in a sheet of paper that old or that might have been exposed to up and down humidity for that amount of time," Lyter said. "There's no guarantee you're going to find everything that's there."
The National Archives is apparently taking Mellinger's proposal to decipher missing parts of Haldeman's notes seriously. But officials with the archives -- a taxpayer-funded arm of the federal government -- are saying little about it, beyond a recent published report.
In a July 28 online article, archivist David Paynter was quoted in "Mother Jones," saying "the reason we are going forward with this is that we've already tried with the tape itself. Here's another avenue to shed light on an important episode in history. It's very exciting."
Denying a request to interview Paynter, the National Archives said in a statement, "From time to time, individuals suggest new technologies to unlock historical mysteries. Senior officials at the National Archives are meeting to evaluate this idea."
When contacted to follow up on the statement, spokeswoman Miriam Kleiman declined to comment, abruptly hanging up the phone.
Paynter referred all questions back to the public affairs office.
Until the National Archives decides whether it will examine Haldeman's notes using electrostatic detection, professional historians and amateurs like Mellinger will continue to speculate on the 18 1/2-minute gap.
"I do it just for the love of the whole thing," Mellinger said of his Watergate obsession. "And once you actually get results, it's very addicting."
For now, the conversation between Nixon -- who would become the first U.S. president in history to resign from office -- and one of his closest aides is still a puzzle.
"People love a mystery," presidential historian Richard Norton Smith said. "We're still debating the Lindbergh kidnapping. We're still arguing over Amelia Earhart and Jimmy Hoffa. So it's not surprising that the 18 1/2 gap should be subject to renewed debate."