Venezuela President Nicolas Maduro goaded opposition leader Juan Guaido during a rally in Caracas on Thursday, taunting his rival for failing to unseat him.
A year ago, parliament speaker Guaido launched a challenge to Maduro's authority by declaring himself acting president, a move backed by more than 50 countries.
But despite initially attracting massive street protests to support his cause -- backed by US sanctions against regime figures -- Guaido's momentum waned over the second half of 2019.
On Thursday, Maduro mocked the "failure of the putschist adventure" and in a message to Guaido he added: "Who the fuck elected you?"
Maduro was re-elected president in 2018 in a vote boycotted by much of the opposition and widely dismissed as rigged.
After Guaido took over as parliament speaker last January, the legislature declared Maduro a "usurper" over his re-election.
It is in his role as parliament speaker that Guaido claims the authority to be acting president.
But earlier this month, Maduro tried to block Guaido's attempts to be re-elected speaker.
When Guaido turned up to parliament for the vote, security forces prevented him from entering and a rival opposition politician, Luis Parra, declared himself speaker in Guaido's absence.
Maduro backed Parra's claim but Guaido says he still has the support of more than half of the opposition-controlled National Assembly.
Speaking from a balcony at the presidential palace, Maduro branded Guaido a "servile idiot" and "traitor."
Guaido flouted a travel ban from Maduro's government to surface in neighboring Colombia on Sunday to meet US Secretary of State Mike Pompeo.
He then moved on to Europe, meeting with British Prime Minister Boris Johnson and EU foreign policy chief Josep Borrell.
He is currently attending the World Economic Forum in Davos, Switzerland.