This story has been updated.

Hillary Rodham Clinton will formally enter the presidential race with an announcement on Sunday followed by appearances on the campaign trail next week, three people familiar with her plans said on Friday, ending months of anticipation surrounding the overwhelming favorite for the Democratic nomination.

Clinton plans to launch her campaign via social media and with a video on Sunday articulating her rationale for seeking the White House. She'll then travel to the first-in-the-nation caucus state of Iowa early next week for campaign events, these people said. She is expected to hold mostly small discussion events with voters designed to help the former secretary of state connect with ordinary Americans and listen to their concerns, forgoing the large rallies and traditional announcement speeches of some of her Republican rivals.

Behind the scenes, meanwhile, Clinton's fundraising machine is revving up. Her top bundlers are plotting aggressive outreach to thousands of Democratic donors over the weekend and into next week urging them to immediately send checks and make donations online as soon as the Clinton campaign's Web site goes live.

Democratic strategists, advisers and fundraisers described Clinton's plans only on the condition of anonymity because she and her team have not yet finalized all aspects of her campaign rollout. Her official spokespeople declined to comment.

Clinton's Sunday announcement would come one day before the expected campaign launch of Sen. Marco Rubio (R-Fla.), who is planning a major speech to supporters on Monday afternoon at Miami's iconic Freedom Tower. Sens. Ted Cruz (Tex.) and Rand Paul (Ky.) are the only two major Republican candidates who already have officially entered the race.

For months, Clinton, like many Republican contenders, has been assembling a campaign-in-waiting. Widely considered by Democrats to be the heir apparent to President Obama, Clinton has hired several of Obama's top campaign strategists to work on her 2016 bid and dozens of staffers, including in the early caucus and primary states of Iowa, New Hampshire, Nevada and South Carolina. Last week, the Clinton team signed a lease on office space in Brooklyn, N.Y., as her national campaign headquarters.

Ahead of the campaign launch, Clinton released a new epilogue on Friday for "Hard Choices," her State Department memoir that is coming out this month in paperback. The chapter touches on an array of issues, from her relationship with Obama to economic mobility to childhood education. She writes about her desire for every American in the 21st century to have an equal and fair shot at economic success, a theme she has highlighted in her public speeches over the past year.

Clinton ends the epilogue by ruminating about a "memory quilt" she received as a gift after her granddaughter's birth: "I wondered for a moment what a quilt of my own life would look like. . . . There was so much more to do. So many more panels waiting to be filled in. I folded up the quilt and got back to work.”

Using a social media launch for her campaign, rather than a boisterous and celebratory rally, is a deliberate attempt by Clinton and her advisers to avoid the pitfalls that tripped her up in her 2008 presidential campaign, when she was heavily favored at the outset but ultimately defeated by Obama. Clinton suffered from criticism then that she appeared as if she felt entitled to the nomination and often came off as flat and uninspired on the stump in front of large crowds.

The go-slow, go-small strategy, Democratic advisers say, plays to her strengths, allowing her to meet voters in intimate settings where her humor, humility and policy expertise can show through.

That approach is modeled on the listening tour she conducted across New York state at the start of her successful 2000 Senate race. Longtime advisers and allies said Clinton wants to reestablish the connection with voters and regular people she had in that campaign, when she traveled into diners and people’s living rooms and kitchens to listen to their concerns.

Jay Jacobs, a former New York Democratic Party chairman and longtime Clinton friend and supporter, said the 2000 listening tour became “a two-way conversation that impressed voters not by just what she said, but by how intently she listened. I think that’s Hillary. That’s something that has worked before, and it’ll work again.”

Jacobs, who recently met privately with Clinton when she addressed his group of the American Camp Association in Atlantic City, N.J., said Clinton’s 2016 presidential campaign will not be “reactive.”

“It will be one that really presents Hillary Clinton to the voters as she is known by people who are close to her: as a very warm, genuine, thoughtful, certainly intelligent, regular person,” Jacobs said. “There’s been so much that we’ve seen that seems to create an image, by the press and by others, those who are looking to derail her, but now the voters are going to hear from Hillary and they’re going to see Hillary.”

Within hours of news reports Friday morning that Clinton would launch her campaign this weekend, the Republican National Committee announced an online ad as part of its "#StopHillary" campaign to highlight scandals over her use of private e-mail at the State Department and foreign donations to her family's charitable foundation.

“From the East Wing to the State Department, Hillary Clinton has left a trail of secrecy, scandal and failed liberal policies that no image consultant can erase,” RNC Chairman Reince Priebus said in a statement. “Voters want to elect someone they can trust and Hillary's record proves that she cannot be trusted. We must 'Stop Hillary.'”

Clinton's fundraising team is standing by for the launch of her Web site, when the campaign can begin accepting donations online. One priority is creating a robust small-donor network similar to the Obama campaign's vaunted list from his 2008 and 2012 campaigns, and Clinton advisers see her announcement period as a ripe opportunity.

“We’re going to have to raise as much money as possible,” said one Clinton fundraiser who spoke on the condition of anonymity to discuss the campaign’s internal plans. “We’re not going to take it slow. The announcement is a good time to raise money, and we’ll have everyone out there asking people to support her candidacy.”

Several Clinton fundraisers described a rush of major donors wanting to get checks in the door on Day One of the campaign.

“All the horses are in the gate just waiting for those gates to open,” said John Morgan, a prominent Florida donor and Clinton fundraiser. “That’s how I describe the fundraising efforts. There’s really nothing to do until the gate opens. But the gate could open Sunday, and it could be the flood gate. The only issue they’ll have is how fast can they raise the money, because the money is pent up. And if they start holding events, the line will be around the block to host an event.”

Clinton's fundraising efforts are being directed by Dennis Cheng, who had been finance director at the Bill, Hillary and Chelsea Clinton Foundation. But the campaign is not expected to give titles to top bundlers or announce a list of finance committee chairs or members, according to Democrats with knowledge of the Clinton strategy.

Clinton’s focus for now will be on raising money just for the primary – with a cap of $2,700 a donor – through Internet appeals. That will free her up to spend time on the trail, talking to voters, rather than wooing wealthy donors at high-priced fundraisers.

“I don’t think the first thing out of the gate she should be doing is a bunch of big fundraising events,” said one senior party strategist.

This is a notable contrast to former Florida governor Jeb Bush, who has spent the better part of four months crisscrossing the country holding closed-door finance events for his Right to Rise political action committee and super PAC with tickets costing as much as $100,000 each.

“I think she’ll be in Iowa eating corn on the cob instead of clinking champagne flutes with donors,” Morgan said. “She can do this much quicker, much more efficiently because she’s not fighting for donors. Rubio, Bush, that whole crowd is in mortal combat for dollars. She’s not. That’s her advantage.”

Without a strong Democratic challenger on the horizon, Clinton does not feel the pressure to match the kind of “shock and awe” fundraising effort that Bush has been undertaking to scare off other Republican hopefuls. “They have the luxury of doing this the right way, and not trying to just see how much money they can hoover up,” the senior party strategist said.

In fact, Clinton’s team is wary of raising too much money too quickly -- creating a bulging war chest that could play to the inevitability theme she wants to avoid this time around.

Clinton will not be able to seed her new campaign with a major cash infusion as she did at the start of her 2008 campaign, when she transferred $10 million from her Senate reelection committee. That helped her post a record $36 million haul for her first fundraising quarter. Her 2008 presidential committee is shut down, and her Senate committee has just $158,000 left in reserves.

But her campaign this time will be able to build on the efforts of Ready for Hillary, an outside group started in 2013 to lay the groundwork for Clinton's campaign, which has held more than 1,000 grass-roots events across all 50 states in the past two years. In the process, the group amassed a donor pool of more than 135,000 people, the vast majority of whom gave contributions of $100 or less, according to super-PAC officials. Ready for Hillary also has cultivated a network of local organizers who could sign on for similar roles with the official campaign.

That could give Clinton a sizable head start over some of her Republican rivals in building a small-donor operation. Ready for Hillary will not be able to coordinate with Clinton once she announces, but it could share its list of supporters with her campaign through a list swap, campaign finance lawyers said.

But the group may not even have to take that step. Once Clinton declares her candidacy, the super PAC can simply direct its supporters to her Web site, allowing her campaign to quickly build a small-donor list.

And once she’s officially in, Ready for Hillary plans to post online the names of hundreds of donors who have given or raised more than $5,000, according to a person familiar with the plans. That list — which includes at least 222 donors who gave $25,000 — would be valuable not just for Clinton’s campaign but for Priorities USA, the high-dollar super PAC planning to finance a pro-Clinton television advertising campaign and now faces pressure to kick-start its fundraising.

Dan Balz and Matea Gold contributed to this report.