First lady Michelle Obama's speech at the Democratic National Convention Monday night is the first of several campaign stops she's expected to make for Hillary Clinton as the two women - distant throughout much of the Obama presidency - find common cause in their campaign to defeat Republican Donald Trump in November.
While the Clinton campaign and the White House declined requests to preview how they intend to deploy the first lady, her overall popularity with Americans and initiatives for military families and against child obesity make her a potentially valuable Clinton surrogate with white, female voters in swing-state suburbs as well as with minority voters in US cities.
Michelle Obama remains more popular than her husband, President Barack Obama, and either major party presidential candidate. She's been viewed favorably by about two-thirds of Americans through most of her husband's two terms in office, according to Gallup poll data.
The most recent Gallup survey, July 13-17, found she was viewed favorably by 58 per cent of US adults and unfavorably by 33 per cent.
Melania Trump's speech to the Republican National Convention last week, with lines that mimicked Michelle Obama's 2008 convention speech, underscored the first lady's mass appeal.
"With her numbers, she can go anywhere," said David Plouffe, Obama's 2008 campaign manager, said of the first lady's utility for the Clinton campaign. "I think she can be super-effective in suburban areas."
Clinton's spokeswoman Jennifer Palmieri said Michelle Obama will be a "highly effective messenger" for the campaign. Clinton's ad campaign includes one featuring children watching clips of some of Trump's statements denigrating people and groups. Palmieri called Michelle Obama a role model and said "few know better than her the importance of electing leaders who set the right example for our children and grandchildren."
An administration official who wasn't authorised to discuss the matter publicly said the first lady in her address, which will wrap up the first day of the convention, will talk about how the president shapes the nation's values and aspirations and Clinton's commitment to equality and inclusion.
Obama's desire to cement her husband's legacy by electing a president who will carry on his initiatives is driving her participation, even as her distaste for campaigning may see her limit the number of appearances and dictate their terms.
"One of the strong attributes Michelle Obama has had is that she does not come across as political," said Jim Hodges, South Carolina's former Democratic governor, who supported Barack Obama in 2008 and is supporting Clinton now. "People believe she's sincere about the issue she's concerned about. The question is how much time she can and will devote to any campaign."
While Clinton is a former first lady herself as well as Obama's former secretary of state, the Clintons and the Obamas haven't socialised over the course of the Obama presidency, nor have the two women developed a bond like the one between Michelle Obama and the vice president's wife, Jill Biden.
"They're not close; they don't talk often," said Kate Brower, author of First Women: The Grace and Power of America's Modern First Ladies, published this year, and a former White House correspondent. "I'm sure she wants Hillary to win, but everybody I talked to for my book said that they had a lot of animosity" that followed them from the 2008 campaign into the White House.
During the 2008 campaign, Clinton mocked Obama's hope-and-change message by saying that "the sky will open, the light will come down, celestial choirs will be singing." Brower said while the Bush administration had continued funding for Save America's Treasures, a programme Clinton had helped initiate during her husband's presidency to preserve historic buildings and art, the Obamas surprised many with their decision not to continue that funding.
One person close to the Obamas, who spoke on condition of anonymity, said the relationship between the Michelle Obama and Hillary Clinton had thawed years ago and has strengthened through conversations about the challenges of raising children in the White House.
While Clinton's ties to the Obama White House run mostly through the West Wing, one of Clinton's top communications advisers is Kristina Schake, a former communications director to Michelle Obama.
And in recent months, as Trump moved toward the Republican nomination and the Obamas' older daughter, Malia, reached voting age, the first lady and the presumptive Democratic nominee have made careful inroads toward one other.
In April, while Clinton and Bernie Sanders were still competing in the Democratic primary and before the Obamas were prepared to make a formal endorsement, the first lady called Clinton an "impressive" and "phenomenal" woman.
"I've gotten to know her, and I think she's made some pretty major contributions over the course of her life," she told children at a "Take our Daughters and Sons to Work Day" event at the White House. "She's devoted her life to public service, as have many people who are seeking the presidency."
When Clinton appeared with President Obama earlier this month in North Carolina, she made a point of praising Obama's wife. "As we went from rivals to partners to friends, my esteem for him just kept growing," Clinton said of the president. "So did my admiration for his brilliant wife, Michelle, and those two amazing daughters that they have raised.
"My husband and I know how hard it is to raise a child in the public eye, in the fishbowl of the White House. But the Obamas have done a fabulous job."
South Carolina's Hodges said, "Where they might have been in a political campaign in 2007 or 2008 is irrelevant at this point. There were able to come together, find a way to serve together effectively and become political allies.
"There is a gratitude the Obamas have for the role she played in the administration and an acknowledgment of her skill," Hodges said of Clinton. "I think there is a genuine admiration that developed from 2008 on."