The money-access-power matrix is that much more visible this year with the rise of the super PACs and politically active tax-exempt groups. Such organizations now rival the formal party apparatus in money and influence, and allow wealthy individuals and corporations to donate unlimited money to political causes, sometimes without having to disclose their identities.

The outside groups raising funds to beat Mr. Obama cannot coordinate their spending with Mr. Romney, but the gossamer-thin federal rules allow them to piggyback on major Romney donor conferences and fund-raisers by sending representatives to mingle with big givers or plan their own events nearby. That will continue in Tampa: American Crossroads, co-founded by Mr. Rove, will host a donor briefing with former Gov. Jeb Bush and Senator Marco Rubio, both of Florida. Restore Our Future, founded by former Romney aides, will hold a briefing for prospective donors this week.

What happens day to day in Washington — fund-raising, lobbying, dining and entertainment — expands to a gigantic scale around the conventions.

“The delegates are like bored teens counting down the minutes until spring break,” said Gabriela Schneider of the Sunlight Foundation, a watchdog group that is sending staff members to Tampa and to the Democratic convention in Charlotte, N.C., to track party attendance. “Lobbyists and big-money sponsors cut through the hype that conventions are about anything else and capitalize on it by throwing hundreds of invite-only events.”

There is a luncheon cruise for Colorado delegates paid for by Federal Express and CH2M Hill, a federal and municipal construction contractor. A cigar tent courtesy of the American Action Network, which will spend millions defending the House Republican majority this year, will shelter smokers at a “Liberty Pavilion.” The Financial Services Roundtable, Wall Street’s leading trade group, will host an invitation-only luncheon for finance executives, members of Congress and regulators, followed by a public forum on how federal policy affects its members’ retirement and annuity products.

“The conventions are obviously the heart of politics,” said Scott Talbott, the round table’s senior vice president for government affairs. “And this is an opportunity to celebrate the political process between members of Congress and the industry.”

Both parties are receiving $18 million in taxpayer funds, money controlled by party officials to put on each convention’s official speeches and nominations. But far more private money flows into each party’s “host committee,” a tax-exempt nonprofit organization that, under a loophole created in the 1980s, can accept unlimited individual, corporate and union contributions and does not have to disclose its finances until October.