WASHINGTON >> Michelle Obama has bridled for years at the confines of life in the White House and has tried to steer clear of the partisan messiness that has consumed her husband and is fueling this year’s bare-knuckled presidential contest.

But this week, Obama will wade into the campaign fray on behalf of Hillary Clinton, putting her broad popularity and reputation for authenticity to work for a candidate who has suffered from a lack of both.

At an event in northern Virginia on Friday, Obama will urge voters to register before the state’s Oct. 17 deadline, the first of what aides say will be a series of appearances in the coming weeks in support of Clinton.

Obama’s steps into the campaign spotlight underscore her transformation from a once-reluctant political spouse into a confident public figure, a role she says she has embraced more fully during President Barack Obama’s second term.

Michelle Obama’s spokeswoman, Caroline Adler Morales, said the first lady’s focus would be on encouraging voters in swing states, particularly young people and African-Americans, to register and vote.

Her message, Morales said, will emphasize “the qualifications and demeanor a president needs, the values we hold dear as Americans and our shared hopes for the future.”

Obama previewed her pitch in July during a prime-time speech at the Democratic National Convention, in which she delivered a testimonial for Clinton as a leader who could be trusted to carry on Obama’s legacy. It was also a quiet but sharp denunciation of Donald Trump, whom she did not name, in which she took aim at his campaign slogan and derided him as a cynic who viewed the world’s challenges in terms of 140-character posts on Twitter.

Obama has never had much affection for the campaign trail, and has spoken openly about trying to persuade her husband not to run for president and her struggles adapting to the scrutiny and obligations of political life. She has strictly limited her appearances at political events during the president’s time in office, agreeing to them only when she believes her presence could have a major impact on a race.

That, Clinton’s advisers say, enhances the first lady’s effectiveness as a voice for their candidate. She is widely known and liked by Americans — her approval rating was at 58 percent in July, according to Gallup — but seen as removed from politics and partisanship.

Michelle Obama and Clinton were once adversaries — Obama took umbrage in private during the 2008 Democratic primary race at Clinton’s criticisms of her husband — but their goals are now inextricably aligned.

Obama “is a very trusted voice who has not seemed to have an agenda, and someone whose husband ran against Hillary and is now a big believer in her, so those words coming from Michelle Obama are especially meaningful,” said Jennifer Palmieri, communications director for Clinton’s campaign.

The first lady has also demonstrated a knack for using pop culture and social media to appeal to the core coalition that propelled her husband to the White House — young voters, minorities and single women. Those elements will also be part of her push for Clinton, aides said, though they declined to detail her itinerary because it is still developing.

“She’s able to speak in an honest and relatable way that the American people can connect with,” said Jennifer Psaki, Barack Obama’s communications director and a strategist on his presidential campaigns.

That is the part of her job that Michelle Obama has always said she relishes the most. Unlike Clinton, a politics junkie and policy wonk who as first lady wanted an office in the West Wing and led Bill Clinton’s health care task force, Obama has avoided hard-edged debates. She has instead prioritized more universally popular causes such as her “Let’s Move” campaign for healthy eating and exercise, the Joining Forces initiative to support veterans and their families, and her “Let Girls Learn” effort to expand educational opportunity for women and girls.

“When Barack was talking about running, I was like, ‘Are you crazy?’ — I mean, ‘would you just, like chill out and do something else with your life,’” Obama told Oprah Winfrey in June during an appearance in Washington. During their discussion, the first lady said she had determined early on to “protect my time” jealously and was looking forward to the day when she could finally leave her home without consulting the Secret Service.

Still, almost despite herself, she has become a formidable force in the campaign.

“She has never loved politics very much, and I don’t think she does right now, but she happens to have become a very savvy politician,” said Myra Gutin, a communications professor at Rider University whose research focuses on first ladies.

“Perhaps being in the White House has sensitized her more,” Gutin added, “and she has become the asset politically that Obama wanted.”

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