Not only is she running, but we have a very good idea of what her campaign will look like.

Hillary Clinton is in the final stages of planning a presidential campaign that will most likely be launched in early April and has made decisions on most top posts, according to numerous Democrats in close contact with the Clintons and their aides.

Campaign advisers say the likelihood of a campaign, long at 98 percent (she never really hesitated, according to one person close to her), went to 100 percent right after Christmas, when Clinton approved a preliminary budget and several key hires.

Most of the top slots have been decided, with one notable exception: communications director, a job that is now the subject of intense lobbying and jockeying among some of the biggest names in Democratic politics. One top contender is White House communications director Jennifer Palmieri, who is close to likely campaign chairman John Podesta.

Numerous lessons from Clinton’s failed 2008 campaign are being baked into the 2016 plan, including a determination to improve relations with the news media — or, at the very least, to have a “good cop” role to help her get off on a better foot with the journalists who will help shape her image.

Reflecting other lessons learned, the campaign is being planned with more of a “big-tent mentality,” as one adviser put it. And Bill Clinton is being integrated from the start, after feeling isolated from parts of her campaign against Barack Obama.

One component of Hillary Clinton’s emerging strategy involves quietly but aggressively courting key endorsers from the left, who could help increase progressives’ comfort level and take the wind out of a potential challenge. Two top targets: Robert Reich, the economist and former labor secretary in her husband’s administration, and Rep. John Lewis (D-Ga.), the civil rights icon. In December, she won public endorsements from former Democratic National Committee Chairman and Vermont Gov. Howard Dean and Sen. Al Franken (D-Minn.).

Bill Clinton is already deeply engaged in the campaign, warning that Jeb Bush is a real threat, while New Jersey Gov. Chris Christie is probably just a sideshow.

The former president got a heads-up from the camp of President George H.W. Bush a few days before former Florida Gov. Jeb Bush made his surprise Facebook announcement in December that he would “actively explore” a campaign. The two former presidents have developed a friendly bond, partly because of their work together on relief for the 2004 Asian tsunami.

The exact timing of Hillary Clinton’s launch is unknown, but close allies expect her to officially enter the 2016 race shortly after the end of this quarter, so that her first fundraising report will be a blockbuster. On March 4, the Clinton Foundation holds its annual gala in New York, with entertainment by Carole King, and it’s expected to be one of the Clintons’ final major events before the campaign.

Friends and advisers say she is planning this campaign “her way,” without being buffaloed by outside pressure.

“She is taking her time,” one adviser said. “Part of doing something right is … taking the time to balance the advice she is getting with her own thoughts. She’s in no rush. People have been putting a red ‘X’ on the calendar for a long time, but that isn’t necessarily happening internally.”

Clinton will enter the Democratic race with a bang — and virtually no opposition to speak of. Sen. Elizabeth Warren (D-Mass.), who could mount a serious campaign from the left, has said she won’t run, and is making no behind-the-scenes preparations. Vice President Joe Biden says he might very well run — but mainly wants his name in the mix in case Clinton implodes.

This leaves a trio of long shots with scant money: Sen. Bernie Sanders (I-Vt.), former Maryland Gov. Martin O’Malley and former Sen. Jim Webb of Virginia.

The potential opposition is so weak that Clinton might wind up not even debating during the primaries, which many Democrats view as a mixed blessing.

The Clinton team knows it can’t campaign with the swagger of a presumptive nominee because the air of inevitability was so damaging last time around. That said, some advisers are already privately talking up potential running mates, with Sens. Michael Bennet of Colorado and Tim Kaine of Virginia dominating the early speculation.

Some advisers expect a push for diversity on the ticket. So the shortlist also is expected to include Housing and Urban Development Secretary Julián Castro, Labor Secretary Tom Perez, Sen. Cory Booker of New Jersey and perhaps California Attorney General Kamala Harris, who is running for U.S. Senate.

Despite the internal confidence, Clinton won’t enter without substantial concerns and obstacles, some of which are self-evident to her top advisers and are a subject of constant conversation among Democrats during the build-up phase.

The Warren wing can be expected to continue pounding her for fat speaking fees and chummy Wall Street relations, and try to pull her to the left in ways that are unnatural for the Clintons. If she were to lurch left, she would risk appearing insincere or baldly political.

These allies also know the past problems of Clinton Inc. that could resurface: the competing Bill and Hillary camps, the questionable donors and backbiting when things get tense or go south. Clinton insiders blame a confused and conflicted ’08 structure for many of her stumbles in that primary race.

The campaign-in-waiting is working to assuage these concerns by creating a coherent leadership structure and bridging the Bill and Hillary worlds. “There’s an enormous amount of coordination and communication that goes on with his office,” an adviser said. “Everybody recognizes that it’s important.”

Here’s the rub: A trio of people with substantial juice will be above campaign manager Robby Mook — with Podesta, who is leaving his West Wing post as counselor next month for a short stay at the Center for American Progress until the campaign formally launches, serving as chairman; longtime family counselor Cheryl Mills serving as a top adviser, regardless of whether she is on the inside or outside (a possible title: co-chair); and longtime close aide Huma Abedin, the most important non-Clinton in her orbit. (When the White House wants to reach Clinton, Abedin gets the call.) Philippe Reines, one of the longest-serving Hillary whisperers, will be another crucial outside adviser.

Toss in Bill and Chelsea, and it’s clear why structure is such a stress point.

Tom Nides, who returned to Morgan Stanley after serving as Hillary Clinton’s deputy secretary of state, will have a top role in the campaign — probably involving high-level fundraising. Dennis Cheng, the Clinton Foundation’s chief development officer, is expected to move over to the campaign in a top finance post.

Advisers know that Clinton neither likes nor trusts the press — and feels that it’s mutual. She remains a voracious consumer of news about herself, occasionally complaining about an article’s tone or omissions.

But she got largely favorable coverage as secretary of state and experienced a press corps that she considered more substantive and less sensational. She visited with reporters in the back of her plane on international trips and discovered they don’t bite. So the campaign plans to include a media-friendly communications official, as a counterweight to the instinctive insularity of Hillaryland.

“You do see what works and address what works the next time around,” an adviser said. “The default isn’t toward the pit-bull mentality.”

In addition to Palmieri, other names that have been in the hopper: Eric Schultz, principal deputy White House press secretary; Brian Fallon, an alumnus of New York Sen. Chuck Schumer’s office who is now the top spokesman for Attorney General Eric Holder; Mo Elleithee, the DNC communications director; Karen Finney, a former MSNBC host and alumna of the Clinton White House; and Kiki McLean, a consultant and strategist who has worked at the top of many national campaigns.

Nick Merrill, who worked with Reines at State and is now Clinton’s spokesman, is trusted and well liked and will remain in the inner circle.

Clinton has recruited two of the top brains of the Obama campaign — pollster Joel Benenson and media strategist Jim Margolis, who worked for her husband’s campaign in 1992. Now that the architecture of the campaign is clear, the two are helping with the next critical task: developing her message.