Ostwald seems to have timed it perfectly. Clinton's speech at the Democratic National Convention created a new generation of fans. A New York Times/CBS News poll afterward gave him a 66 percent favorability rating, higher than at any time during his presidency, which was roiled by the Monica Lewinsky scandal and his subsequent impeachment by the House (but acquittal by the Senate).

The speaker series won't say what it is paying for Clinton's appearance, but he clearly is doing well on the circuit.

A CNN analysis of Hillary Rodham Clinton's financial disclosure statement last summer – required for her position as secretary of state – found he pulled in $13.4 million in 2011 and has earned $89 million giving speeches since he left office in 2001.

And he isn't just preaching to older Democrats nostalgic for bygone days or people wearing the "I Miss Bill" buttons that were so popular during the presidency of George W. Bush.

Elli Brennan, a 17-year-old senior at Rio Americano High School, will be in the audience Tuesday along with a handful of fellow students from the school's Civitas political science program.

"I saw his speech at the convention and I thought that was definitely one of the highlights of the entire campaign," said Brennan, who paid $60 for a discounted ticket to see Clinton.

One reason for Clinton's popularity at giving speeches is simple. He's good at it.

Schnur, a longtime Republican operative, recalls going to see Clinton speak a decade ago at the Dorothy Chandler Pavilion in Los Angeles.

"It's an audience of thousands and thousands of Westside Democrats, and there's Bill Clinton giving an extraordinary speech, and I'm probably clapping more than anyone in the audience.

"He gave a 55-minute speech off of notes that appeared to be written on the back of a business card."