Carly Fiorina, former head of Hewlett-Packard, photographed in September in Washington. (Bill O'Leary/The Washington Post)

On a Republican presidential debate stage expected to be filled with more than a dozen current and former politicians, Carly Fiorina envisions herself standing out — as the only woman and the only CEO.

Sensing an opportunity in a crowded field that lacks a front-runner, the former Hewlett-Packard chief executive is actively exploring a 2016 presidential run. Fiorina has been talking privately with potential donors, recruiting campaign staffers, courting grass-roots activists in early caucus and primary states and planning trips to Iowa and New Hampshire starting next week.

Fiorina, whose rise from secretary to Silicon Valley corporate chief during the dot-com boom brought her national attention, has refashioned herself as a hard-charging partisan hoping to strike a sharp contrast with the sea of suited men seeking the GOP nomination.

But Fiorina, 60, has considerable challenges, chiefly that she has sought but never held public office. Lingering disarray from her last campaign could also haunt her next one, undercutting her image as an effective manager. Fiorina still owes nearly $500,000 to consultants and staffers from her failed 2010 Senate bid in California — debts that have left some former associates bitter.

Privately, several prominent Republicans spoke about Fiorina with disdain, saying she has an elevated assessment of her political talents and questioning her qualifications to be commander in chief.

Former Hewlett-Packard CEO Carly Fiorina addressed the crowd at the 2014 Conservative Political Action Committee in March, where she discussed her views on leadership. Fiorina is exploring a potential 2016 presidential run as a Republican. (The American Conservative Union)

But allies defended Fiorina’s credentials, saying she would make a strong contender.

“She’s very articulate, she’s very thoughtful and has a very positive message,” said David Carney, who has been a top strategist for past GOP presidential candidates and whose wife worked with Fiorina this year in New Hampshire. “She’s got just as much of a record of accomplishment and a story and ideas as anybody else who’s running.”

Carney drew a comparison between Fiorina, a free-market advocate, and Sen. Elizabeth Warren (D-Mass.), a populist firebrand: “She’s sort of the antidote to the Elizabeth Warren arguments from the left.”

In June, Fiorina started the Unlocking Potential PAC with a mission of galvanizing female voters and beefing up the GOP’s ground game. The super PAC made modest investments in four Senate races while funding Fiorina’s travel to presidential battlegrounds such as Colorado, Iowa and New Hampshire. “She left people wanting more,” said Angie Hughes, the group’s Iowa director. “We did a lot of things that would be helpful to anyone wanting to run for president.”

This month, Fiorina sent handwritten notes to some Iowa activists thanking them for their help with her super PAC and looking forward to “the next phase.”

Asked this month on NBC’s “Meet the Press” about her 2016 plans, Fiorina said: “When people keep asking you over and over again, you have to pause and reflect. So I’ll pause and reflect at the right time.”

Fiorina plans to visit New Hampshire in early December to address a group of businesses chaired by Rep.-elect Frank Guinta (R-N.H.) and return to Iowa in January to address the Iowa Freedom Summit, co-hosted by Rep. Steve King (R-Iowa) and the group Citizens United. In February, Fiorina will address the Conservative Political Action Conference in Washington.

Helping Fiorina chart her political future are consultants Frank Sadler, who once worked for Koch Industries, and Stephen DeMaura, a strategist who heads Americans for Job Security, a pro-business advocacy group in Virginia.

Since her Senate bid, Fiorina has moved to Virginia, living with her husband, Frank, in Lorton. Her advisers, who requested anonymity to speak candidly, said she is taking the steps necessary to prepare for a presidential campaign.

One adviser said that “the challenges are obvious” but that Fiorina sees an opportunity to run as a “non-politician offering a unique perspective.” The adviser added, “She certainly has the fire in the belly to be involved.”

Fiorina declined through an adviser to be interviewed.

Some prominent Republicans said it would be helpful for the party to have a woman running for president, especially considering the expected candidacy of Hillary Rodham Clinton on the Democratic side. But they questioned whether Fiorina is the right woman.

At Hewlett-Packard, Fiorina was a pioneering executive — the first female CEO of a Fortune 50 company — but her high-profile tenure was controversial. In 2005, after a merger with Compaq, she was forced to resign.

After serving as a prominent surrogate for Sen. John McCain (R-Ariz.) in his 2008 presidential campaign, Fiorina made her first run for elected office in 2010, challenging Sen. Barbara Boxer (D-Calif.). She staked out conservative positions to the right of California’s mainstream — opposing abortion rights and efforts to cut greenhouse gases, for example — and lost to Boxer by 10 points.

Reed Galen, a California-based Republican strategist, said Fiorina is “obviously very interesting, very dynamic and, as one of the first female CEOs, has a good story to tell.” Asked to describe her base within the GOP primary electorate, Galen said: “I’m not sure. My inability to answer shows you how hard a road she has.”

Fiorina will also have to contend with questions about the post-election management of her 2010 campaign committee.

The organization, Carly for California, still owed vendors nearly $500,000 as of the end of September, according to Federal Election Commission filings. The committee’s outstanding debts included more than $80,000 to strategist Martin Wilson and his former firm; $43,000 owed to D.C. law firm Patton Boggs, where campaign counsel Benjamin Ginsberg worked at the time; $36,000 to fundraiser Renee Croce; $5,000 to press aide Jennifer Kerns; and $7,500 to political director Jeff Corless.

The Fiorina campaign also owed $30,000 to Joe Shumate, a storied political strategist in California who served as Fiorina’s senior adviser and died one month before Election Day in 2010.

Fiorina “hasn’t really communicated with anybody in 18 months about how she intends to deal with the campaign debt,” said Wilson, now a vice president at the California Chamber of Commerce. “Hopefully, if she gets more serious about running for another office, she’ll revisit the issue and get some of those bills paid off.”

When Fiorina declared her candidacy for Senate in 2009, she filed paperwork pegging her net worth at between $30 million and $120 million. She donated $5.2 million to her campaign and lent it an additional $1.5 million, for which she was repaid, according to FEC records.

Fiorina’s new Unlocking Potential PAC has raised $1.7 million in less than five months, mostly from a small number of wealthy donors who wrote five- and six-figure checks.

The super PAC spent less than half its funds directly on campaign activity, making $512,000 in independent expenditures in Senate races in Colorado, Iowa, New Hampshire and North Carolina, according to FEC data compiled by the Sunlight Foundation. Its biggest investment was in Iowa, where the group spent a little more than $200,000 on ads, phone calls and staff to boost Republican Joni Ernst.

Meanwhile, the Unlocking Potential PAC spent $333,000 on consulting fees through mid-October, paying a dozen different vendors for fundraising, media, research and political strategy services, according to FEC data analyzed by The Washington Post.

Allies warned that Fiorina needs to consider the difficult mechanics of running a presidential campaign before jumping in.

“There will always be professionals out there looking to land the golden nugget of politics, which is a presidential campaign, and they’ll be whispering sweet nothings in your ear, but you’ve got to come up with that $20 million or $30 million,” said Al Cardenas, a former chairman of the American Conservative Union.

But, he added, “by virtue of the fact that she’s a credible national figure and the only woman candidate out of 19, she should get her due attention at the outset.”

Correction: An earlier version of this article misspelled the last name of the late political strategist Joe Shumate. This version has been corrected.