Extremely discreet in the White House and even more reserved since leaving Washington, Melania Trump is keeping observers guessing whether she will appear, however warily, on the campaign trail alongside her husband.

Aloof and enigmatic, the Slovenian-born former model has been noticeably absent as husband Donald Trump makes his third bid for the White House.

Nor has she attended any court hearings with her husband as he navigates a myriad of cases.

His first criminal trial begins on Monday, and her plans remain unclear.

Her absences are unusual in the United States, where the norm is that politicians' spouses show solidarity in times of crisis -- and they have fueled incessant rumours about the couple's relationship.

'Stay tuned'

In early April, Melania Trump accompanied her husband to a major fundraising event at which Republicans raised more than $50 million for his presidential campaign.

And on April 20, she is to take part in a fundraiser for a group of LGBTQ conservatives, the so-called Log Cabin Republicans.

It is hard to tell whether the former first lady is starting to make minimal appearances in order to cut short speculation about the couple or out of a desire to help her spouse win back the White House in November.

For Katherine Jellison, a history professor at Ohio University and specialist in presidential couples, the fundraiser appearances illustrate a significant shift by Melania Trump.

"These are only a few appearances, but they seem to be signs that she is easing her way back into public life -- and into the Trump campaign," Jellison told AFP.

Melania Trump herself had hinted at such a comeback in a very brief exchange with journalists in mid-March.

"Stay tuned," she said with a smile, wearing large dark glasses.

Melania versus Jill

According to Jellison, the former first lady might prefer events like the ones she's attending in April.

"She seems most comfortable doing these events rather than the more typical campaign activities for a political spouse -- shaking hands and making small talk with a crowd of voters," Jellison said.

That style, she believes, is more suited to Jill Biden, whose husband, President Joe Biden, is Donald Trump's Democratic rival in the November election.

Jill Biden regularly crisscrosses the country, unafraid to venture into hotly disputed states. And in early March, she launched an initiative to mobilize women voters.

Melania Trump on the other hand has not had an easy time with her previous major public appearances.

Her speech to the 2016 Republican nominating convention was ridiculed, and not without merit: Entire passages were lifted from a speech by former first lady Michelle Obama.

She also faced criticism on trips undertaken as first lady, notably when she visited newly arrived migrant children in a shelter near the border with Mexico.

She wore a jacket with the message "I really don’t care. Do U?" written on the back.

She since has been sparing and cautious in her public appearances.

She did emerge from her silence in a rare interview in 2018. When asked about her husband's presumed infidelity with porn star Stormy Daniels, she assured the questioner that she had "much more important things to think about."

It was the hush money payments Donald Trump authorized to the adult-film actress, shortly before the 2016 election, that led to his first criminal trial.

Jury selection starts Monday in New York. With Melania or not, the ex-president is expected to be in attendance.