Democrats are sounding the alarms over the potential turnout at a planned protest in the nation's capital Saturday by opponents of President Obama's domestic policies, but protest organizers say the Democrats' numbers don't add up.

The demonstration is part of the Tea Party Movement and the culmination of a 34-city, 7,000-mile bus tour that began Aug. 28 in Sacramento, Calif. The "partiers" want any health care reform to create more competition and be guided by market principles, not a government-run plan.

D.C. police are closing streets on Pennsylvania Avenue between 14th and 3rd St. NW as protestors march from Freedom Plaza to the National Mall, where there will be a rally.

But there is some confusion over how many people will show up, and where Democrats are getting their estimates. A House leadership aide warned fellow Democrats in a memo obtained by FOXNews.com that up to 2 million people may attend.

"It looks like Saturday's event is going to be a huge gathering, estimates ranging from hundreds of thousands to 2 million people," Doug Thornell, an aide to Rep. Chris Van Hollen, D-Md., wrote, noting that a demonstration held Thursday turned into an impromptu rally for Rep. Joe Wilson, who has come under fire for his outburst during Obama's nationally televised speech to a joint session of Congress

Conservatives have seized on this memo as proof Democrats are playing an expectations game. They say the House leadership wrote the memo in hopes it would be leaked and inflate expectations for the turnout anticipating that it will fall short.

"It's an old political tactic to get out in front and make wild projections and when they're not met, claim their opponents don't have the juice," said Pete Sepp, a spokesman for the National Taxpayers Union, one of the organizers of the rally.

Sepp said there's only one reason to float a number that high.

"You set the bar at 2 million and anything under it becomes a failure," he said, adding that any event in D.C. that attracts 50,000 is considered a success.

A crowd of 2 million people, he said, "would exceed our wildest dreams."

Even President Obama didn't attract 2 million people to his inauguration, when estimates ranged from 1.2 million to 1.8 million people.

But Thornell told FOXNews.com that he was not playing an expectations game and that he simply used the numbers cited by organizers.

"I was using their own words and predictions and estimates," he said, explaining his memo was a compilation of statements from different Tea Party Web sites.

Thornell said he wrote the memo in response to inquiries from Capitol Hill staffers about the rally.

"If you read the memo, it doesn't convey any feeling about this event at all," he said. "I think the memo speaks for itself. … It's not about setting expectations."

FreedomWorks, the lead organizer who has largely bankrolled the rallies leading up to Saturday's march in Washington, D.C. has said it is expecting tens of thousands to attend. Adam Brandon, a spokesman for FreedomWorks, told Politico he expects the crowd to be in the 20,000-30,000 range.

In a blog post, Brendan Steinhauser, the nonprofit group founded in 1984 by former House Majority Leader Dick Armey, quoted Morton Blackwell who said "You should underpromise and overachieve."

"That is what we are trying to accomplish by not giving the media any crowd estimates that they use against us," Steinhauser wrote. "We want to surprise them and shock the nation by the massive turnout that we expect on 9-12. I can only ask you to trust our judgment in this, and promise you that we will have a huge turnout."