By appointing the widely-respected Khaled Bahah as his deputy, Yemen's president and his Saudi backers seek to shore up a government-in-exile whose legitimacy is central to Riyadh's military campaign against Iran-allied Houthi rebels.
While President Abd-Rabbu Mansour Hadi is seen as ineffectual and lacking support even in his embattled hometown of Aden, the last city nominally under his control, Bahah commands admiration across much of Yemen's political spectrum.
"Khaled Bahah is beloved of everyone. He's a strong man - the opposite of Hadi, whose weakness led the Houthis to take control of most of the country," said Mohammed Hazam, a civil servant in Sanaa.
For Riyadh, which has invested its role as a regional leader in a bombing campaign ultimately aimed at restoring the government Hadi represents, it is growing ever more important to bolster his credibility as Yemen's lawful president.
Saudi airstrikes are intended to weaken the militia and force it to return to talks with Hadi's government, which the Houthis do not recognise. There are also efforts to persuade tribes and military units working with the Houthis to change sides.
But nearly three weeks after he fled to Saudi Arabia, Hadi's nominal legitimacy inside his country appears to be increasingly in question, and the president himself has not spoken in public since the Arab League summit in Egypt on March 28.
Even inside Aden, where Saudi airstrikes and weapons drops are aimed at helping the Popular Committees militias fight off the Houthis and their allies in street battles, those manning the barricades do not see themselves as Hadi loyalists.
"In Aden there is no state and no army, and no authority and no president. There is no government. That is the view of the fighters. They are defending their streets and their country," said Wassim al-Sayad, 40, an Aden resident who has taken up arms against the Houthis.
The stakes are high for Saudi Arabia, which faces the prospect of greater influence from arch-rival Iran in its southern neighbour if the Houthis are not neutralised.
Silent footage of Bahah's swearing-in, filmed by a Saudi government cameraman for distribution to media, showed Hadi accepting his vice president's oath in Yemen's Riyadh embassy, and appeared partly to be aimed at winning over Yemeni opinion.
Hadi's Foreign Minister Reyad Yassin Abdulla told Reuters Bahah's appointment would help bolster the government in exile, but he rejected the idea that it was hard to maintain legitimacy while outside the country.
"This is a very temporary situation and it is not our choice. We will do our best to go back as soon as possible to any part of Yemen, hopefully Aden, hopefully in the coming few weeks," he said.
Abdulla compared the situation of Hadi's government to that of Kuwait in 1990-91 during Iraq's occupation to show that legitimacy could be sustained even during a months-long absence.
The foreign minister, who was appointed after Hadi left Aden, said Bahah's appointment meant the government as a whole was more sustainable. "Legitimacy is a continuous thing. It is not about one person, it is about the whole government, the whole state," he said.
Under Yemen's existing constitution, in the absence of a vice president the presidency would pass to the speaker of parliament, who is now in Houthi-controlled Sanaa, if anything happened to Hadi.
"His appointment has opened the door to a political solution to the current crisis in Yemen. He is an independent person," said Ali Mohammed Yahya, a political writer in Aden's Khor Maksar district, a scene of heavy fighting over the past week.
Hadi's internationally recognised government was unpopular even before the Houthis seized control of Sanaa last year, and since his official two-year tenure ended in 2014, his legal status as president was already legally ambiguous.
He was elected, unopposed, in 2012 as an interim president to oversee a two-year shift from former president Ali Abdullah Saleh towards democracy after a 2011 uprising, but while the transition process faltered, he stayed on in power.
Saudi Arabia and its Western supporters want to resurrect that 2012 transition plan, which it and Gulf Arab allies brokered, and which was interrupted by the Houthi advance on Sanaa last year aided by Saleh and his loyalists.
But Hadi's personal lack of popularity, let alone a regional, tribal or military support base, has complicated that ambition.
An army officer in the former South Yemen, he backed the wrong side in internal fighting in 1986 and fled north to Sanaa, before leading northern forces against southern separatists in the 1994 civil war, securing a position as Saleh's deputy.
By contrast, Bahah carries very little embarrassing historical baggage, having backed the popular uprising that unseated Saleh and served as Yemen's ambassador to the United Nations. He was named prime minister by Hadi in November but quit when the Houthis besieged government offices in January.
"There is a way out with appointing Bahah, who is really respected, even by the Houthis. He has since the beginning tried to stay away from aggressive discourse," said Laurent Bonnefoy, the author of Salafism in Yemen.