TAMPA -- The Republican National Convention, which got into full swing here Tuesday, and next week's Democratic version in Charlotte, will be the two most expensive, extravagant pairs of political conventions in U.S. history. 

And most of the fun is paid for by the big corporations, lobbyists and superrich "superdonors" who began arriving in Tampa on their private jets this weekend. 

"This is a system where there's no shame," said Harvard Law professor Lawrence Lessig, an expert on the role of money in politics.  Instead, said Lessig, "There's pride." 

The real VIPs at the conventions aren't the politicians, but the moneymen, explained a man who was once of them. " They're people who want something back," said Jack Abramoff, who served 42 months on fraud, tax evasion and bribery charges. " They're doing it because they have an agenda." 

AT&T, which seeks government approval to charge consumers for expanded use of the internet, took over a restaurant across the water from the Tampa Convention Center to entertain public officials and other VIPs all week. 

When ABC News showed up, employees first tried to hide the sign with the honored guests' names.  The manager then threatened to call police if the cameras weren't turned off. 

Even Isaac's wind and rain couldn't put a damper on the big-money private gatherings, including a performance by the Commodores organized by Senate Republicans. 

Six grateful senators, including John Cornyn of Texas, chair of the National Republican Senatorial Committee, were on hand to thank the corporate sponsors that put up as much as $25,000 a piece to be there.  Cornyn took the stage to thank Blue Cross Blue Shield, AFLAC, and AT&T.

Blue Cross Blue Shield and AFLAC have a stake in health care laws.  The Republican senators they spent time with at the party will play a big role in deciding what does and does not becomes law, and whether the Affordable Care Act, also known as Obamacare, is overturned. 

When ABC News asked Sen. Roger Wicker of Mississippi at the party if he thought lobbyists spent money to get access to politicians, he first said, "I don't know, I don't think so," and then said, "It's an interesting question, which you should ask." 

"It costs a lot to run a campaign," said Sen. Wicker, but did not elaborate.  He said the parties were really to entertain the "young volunteers" involved in the campaign, but also said he missed the days when conventions had more "substance." 

Ellen Miller, executive director of the watchdog group the Sunlight Foundation, agreed with Wicker that the original purpose of the conventions was no longer operative. " The conventions used to have a fundamental role in the selection and election process of the country," said Miller. 

But the conventions, said Miller, still have a purpose. " They're just opportunities to be wined and dined by big corporate America, and to have opportunities to curry favor with individual members of Congress." 
"It's not about just having a good time," said Miller. " It's really about having the ability to cozy up to people who are important to you and to your business.