Yet the party's just beginning. The candidates' own lavish conventions and invitation-only events may be the ultimate display of the corporate coziness they say they're against, CBS News investigative correspondent Sharyl Attkisson reports.
To prohibit unfair influence, it's illegal for corporations to give directly to politicians, campaigns or political parties. But under a giant loophole, corporations can give unlimited money to the political conventions.
And the politicians expect it.
Corporations donate to so-called convention "host committees" that are supposed to be bipartisan and separate from the campaign. In reality, they're run by party leaders who produce brochures selling political access.
Corporate clout at the conventions is now so institutionalized and blatant; it's a $100 million business.
"You know, essentially, it's an extortion game," said Steve Weissman, of the Campaign Finance Institute.
Weissman is a campaign finance watchdog who says powerful party leaders drive the convention fundraising machine.
"They go to these companies and they say 'We want you to give us this money,'" Weissman said.
There's no doubt what was for sale when Minnesota's Governor, Republican Tim Pawlenty, appealed to 110 business leaders for donations for the Republican convention.
His talking points, obtained through a Freedom of Information Act request, said corporate bigwigs would get the chance to "connect with influential government officials ... such as cabinet members, the president, next president."
"He's soliciting donations?" Attkisson asked.
"Yes, he's telling them he expects the Fortune 500 companies to give at least half a million to a million," Weissman said.
Originally, the top package included invites to a "private reception," "private dinner" and "golfing" with Republican leadership. Those perks were later changed to generic language.
For the Democrat's convention in Denver, corporate sponsorship packages start at the "Mile High Plus" Level for $52,800.
There's the "Gold Level:" $250,000 buys "invitations to private events" with key party leaders. That translates into a possible chance to rub shoulders with the likes of House Speaker Nancy Pelosi or Obama himself.
And the very best benefits go to "Presidential Level" donors of $1 million-plus.
All of which seems to defeat the noble idea of keeping corporate influence at bay.
Sens. Obama and McCain have each said convention finance reform will be a priority should he elected.
But that's for another time. For now - it's party on.