The new donor packages mark the latest major erosion of campaign finance limits and are reminiscent of the 1990s, when the parties were flush with huge "soft money" contributions from rich backers and corporations.
The new push further elevates the uber-wealthy at a time when independent big-money groups known as super PACs are dominating the 2016 presidential race.
"This makes the parties more indebted to a handful of very large donors giving beyond the means - or even the imagination - of most Americans," said Trevor Potter, a Republican election law lawyer who favours stricter campaign finance rules.
Officials have been quietly briefing top financiers on the details at gatherings such as the DNC's summer meeting in Minneapolis and Republican leadership conference on Mackinac Island in Michigan.
Veteran campaign bundlers are astonished at the rapid inflation. Just four years ago, the most a donor could give a national political party was US$30,800.
"I think it's terrible," said New York venture capitalist Alan Patricof, a longtime Democratic fundraiser and major Clinton backer. "You're going to have a very, very limited number of people who are going to be able to do that figure."
For Clinton, participating in the new fundraising regime may complicate her call for an overhaul of the campaign finance system - one she renewed yesterday at the New Hampshire Democratic Party convention. Last week, her campaign filed paperwork vastly expanding its joint fundraising committee with the DNC to include 33 state parties - making her the only 2016 candidate so far to set up such a vehicle.
But many donors in both parties are relieved the parties are seeking jumbo-sized contributions again, hopeful they will siphon off some of the funds ballooning the coffers of super PACs.
"I prefer to give to the party, and I think it's a good option for those who don't believe in super PACs," said Robert Wolf, a major Wall St fundraiser for Democrats.
Allies hope the parties can regain their primacy by stockpiling more cash under the control of their eventual presidential nominees - resources that can go directly into voter outreach and field organising.
"This will help stop the uncontrollable flow of non-transparent money and it will help rebuild the parties," said Rick Hohlt, a longtime Republican fundraiser and Washington lobbyist.
The dramatic pricing surge has been driven by a combination of two significant legal changes: the 2013 Supreme Court McCutcheon v Federal Election Commission decision that did away with a cap on how much a political donor could give in an election cycle, and an expansion of party fundraising tucked into an appropriations bill last December.
Together, they have eroded fundraising constraints set by the McCain-Feingold Act, a landmark 2002 campaign finance overhaul aimed at ending the parties' soft money excesses.
Many of the law's provisions still remain, such as the ban on corporate money. But the parties are fully exploiting their new advantages, said Robert Kelner, an election law lawyer who represented the national committees in their challenge to the 2002 law.
Whether power will now tilt away from super PACs remains an open question. Some fundraisers believe donors will prefer to write major cheques to the national parties, which can offer them better access to candidates and convention events.
But officials with Priorities USA Action, the main super PAC backing Clinton, said they do not see the party fundraising as a threat. The group has received US$25 million in commitments since July 1 and is pursuing donors who can give US$1 million and more.
"I don't expect it to have an impact on Priorities' efforts and it hasn't changed the positive response we are getting from folks," said Guy Cecil, the group's senior strategist.
Only a rarified group can play at the parties' new top levels.
The RNC is pitching its Presidential Trust programme, chaired by Representative Paul Ryan of Wisconsin, as a way for "the most elite RNC investors" to help build infrastructure for the general election, according to a description obtained by the Washington Post. Couples who give US$1.34 million this cycle will get to "influence messaging and strategy" through exclusive party leadership dinners and quarterly retreats, among other events.
An invitation to the upcoming RNC finance committee autumn retreat and gala at Washington's Mayflower Hotel notes that donors will be assigned to separate "club dinners" at local restaurants depending on their level of giving.
The RNC, which set up the new fundraising levels at the beginning of the year, is already reaping the benefits. The party has pulled in more than US$71 million to the end of August and is on track to raise a record amount in the 2016 cycle, officials said.
The DNC has been slower to take advantage of the new fundraising landscape, raising US$42.4 million so far this year. Now it is racing to catch up.
Last month, the Democratic Party rolled out three high-level fundraising packages to bring in money before next year's presidential convention in Philadelphia.
Donations to US political parties
2016: US$334,000 maximum donation by individual to a national party per year
2012: US$30,800 by individual to a national party per year
- additional reporting Bloomberg
