On that spring day when she announced her candidacy for mayor in front of her childhood home in Northeast Washington, Muriel E. Bowser was a D.C. Council member in her second term, unknown to vast portions of the city she hoped to lead.

Twenty months later, after enduring two contentious campaigns, Bowser is the District’s mayor-elect, crowning a swift rise that her opponents viewed as improbable from the start.

No doubt Bowser benefited from a federal investigation that crippled the reelection campaign of Mayor Vincent C. Gray (D), whom she trounced in April’s Democratic primary.

Bowser also possessed a significant edge as an African American Democrat in a city in which registered Democrats account for 76 percent of the electorate and blacks are nearly half the population.

Yet, for all her advantages, Bowser, 42, also demonstrated an unwavering discipline as a candidate, assembling an experienced campaign operation, avoiding mistakes and holding her own as a debater.

If she wasn’t always the most riveting candidate, if she invited criticism for not delineating a detailed vision of the future, Bowser offered enough to beat a gaggle of far more experienced opponents, including fellow Council member David A. Catania (I-At Large) and Carol Schwartz (I).

“Whether it was a debate, rally or the first day of early voting, wherever I went she was able to turn out 10 times more people than all the other candidates put together,” said Council member Jack Evans (D-Ward 2), who lost the primary to Bowser after mocking her for what he said was a thin record. “That created an excitement around her campaign.”

As important, perhaps, is that the city is prosperous, with construction cranes looming downtown, crime rates stable and home values rising. More than 65 percent of Washingtonians approved of the city’s direction, a poll found in September.

As an African American Democrat in a city that has elected only black Democrats as mayor, Bowser personified continuity. Her leading rival, Catania — a white, openly gay former Republican — represented a challenge to the status quo.

“On Day One, Everything Changes” read the signs Catania’s campaign hung in the final hours.

“What if people thought the only change they needed was to get rid of Vince Gray?” said Howard Croft, a Democratic activist. “Once you did that, things were moving in the right direction. People weren’t looking for a person to come in and smash everything and start anew.”

Like the Democrats who opposed her during the primary, Catania portrayed Bowser as an unaccomplished lawmaker who did not possess the gravitas to lead the nation’s capital.

Local election results

Yet, Catania failed to present a platform of his own that compelled enough Democrats to embrace him. At the same time, Bowser was able to stir doubts about her opponent, with references to his Republican roots and combative temperament.

“In an overwhelmingly Democratic city, it’s hard to knock out someone who is viewed as coming from the family,” said Bryan Weaver, a community organizer. “At some point, you have to come up with a transcendent theme to trump all that, and David wasn’t able to do it.”

‘She kept her head down’

Bowser announced her candidacy in March 2013, but, in a sense, her campaign began eight months before, when she called for Gray’s resignation amid the probe into his 2010 campaign.

By then, scandals had forced the resignations of two of her council colleagues, and a third would plead guilty to bribery charges. While the council was awash in disturbing revelations, Bowser remained in the background, positioning herself as an alternative to Gray.

“She did nothing extraordinary; she kept her head down,” said Chuck Thies, Gray’s former campaign manager. “There were bodies falling constantly, and here was Bowser, unscathed, untarnished.”

At the same time, she inherited a troupe of political operatives who had worked for former mayor Adrian M. Fenty, her patron who had anointed her as his Ward 4 council replacement when he became mayor.

Adopting Fenty’s green campaign colors and his passion for retail politics, Bowser projected the image of an energetic campaigner with her door-knocking and canvassing. Bowser’s team scored its first breakthrough last winter, during the primary, when it won the Ward 8 straw poll, beating Gray in his base.

“That was the pivotal moment,” Evans said. “That gave her credibility as someone who could win.”

The more monumental twist occurred in March, just before the primary, when federal investigators implicated Gray in a scheme to funnel illegal donations to the mayor’s 2010 campaign.

Almost immediately, Gray’s lead in the polls vanished.

“It was like a tidal wave came under our feet and pushed 90 percent of our support to Bowser,” Thies said. “So she won the primary.”

During the general election, Bowser appeared to eschew attention, spending the summer raising money, building her campaign operation and ignoring Catania.

Civic activists criticized her for agreeing to only four debates. When she released her platform, it was only by e-mail. Catania, in contrast, unveiled a 126-page platform at a news conference, using the moment to pound his theme that Bowser lacked vision.

But the criticism hardly made a dent in the polls, most of which showed her with a double-digit lead.

“She spoke of a vision of the city but didn’t get bogged down in the details,” Weaver said. “What she did was not offend anyone.”

Because Bowser provided few specifics, a sense of uncertainty exists over what policies she will pursue as mayor. “We don’t know her priorities and she wasn’t challenged in the election to do that,” Croft said. “She hasn’t articulated a strong vision beyond the platitudes.”

Charles Wilson, a Ward 8 activist who supported Gray in the primary, said he sees one immediate priority: focusing on black voters still angry that Gray did not win reelection.

“People never saw a kiss-and-make-up between Gray and Muriel Bowser,” he said. “The fact that there wasn’t any unity allowed that bitterness to permeate throughout the general election.”

As a Fenty protege and as the Democrat who vanquished Gray, Bowser knows that Washingtonians can be fickle about their city’s leaders. Of the District’s six mayors, only two have lasted more than one term.