As US President Donald Trump faces impeachment hearings, attention has turned to who would take his place in the unlikely event he is removed from office.
According to the US constitution, the Vice President - in this case, Mike Pence - is the direct successor of the president if they are no longer able to serve.
But what happens if the Vice President is unable to step up to the plate?
This question was brought to the fore on Wednesday after damning testimony from the US ambassador to the European Union, Gordon Sondland, appeared to implicate Mr Pence, along with Mr Trump and Secretary of State Mike Pompeo, in a "quid pro quo" arrangement with the Ukrainian president.
Nancy Pelosi announces a formal impeachment inquiry into Donald Trump. Source: AAP
Twitter was quick to react to the news Mr Pence could too face impeachment proceedings for his part in the alleged arrangement and the hashtag #PresidentPelosi, referring to Democratic House Speaker Nancy Pelosi, was trending.
And a Pelosi Presidency is not out of the realm of possibility.
In the event that both the President and Vice President are unable to lead the country, section 19 of title 3 of the United States Code states that the speaker of the House of Representatives is next in line.
Former chief White House ethics lawyer, Richard Painter, tweeted on Wednesday that impeachment proceedings against Mr Pence were a possibility.
"In a few weeks the only open question should be whether the evidence is sufficient for President Pence to be impeached by the House and removed by the Senate," he said.
Mr Sondland told the House of Representatives Intelligence Committee, which is taking the lead in the impeachment inquiry, on Wednesday that Mr Trump's personal lawyer Rudy Giuliani's efforts to push Ukrainian President Volodymyr Zelenskiy for investigations into the President's political rivals "were a quid pro quo for arranging a White House visit" for the Ukrainian leader.
The inquiry focuses on a 25 July phone call in which Mr Trump asked Mr Zelenskiy to carry out two investigations that would benefit him politically including one targeting Democratic political rival Joe Biden. The other involved a debunked conspiracy theory embraced by some Trump allies that Ukraine, not Russia, interfered in the 2016 US election.
"I think we know now ... that the knowledge of this scheme was far and wide and included among others Secretary of State Pompeo as well as the vice president," said Adam Schiff, the Democratic chairman of the intelligence committee, referring to Mr Pence.
It is only the fourth time in US history that the House of Representatives has started a presidential impeachment inquiry.
Mr Trump has denied any wrongdoing, called the inquiry a witch hunt and assailed some of the witnesses including current White House aides.
