Meanwhile, the polls indicated that support for impeachment has shifted markedly, with most Americans now supporting it.
The pro-Kremlin Russian political and media establishment have grown increasingly skilled at spinning stories to highlight US political weaknesses.
Investigations often damage the president's approval rating, particularly if the inquiry drags on for a long time. But that may not matter to a historically unpopular president like Trump.
As the impeachment inquiry gathers pace, both sides seem to be digging in. What happens in the inquiry in the next few months will have a huge impact on the 2020 presidential election.
President Trump solicited foreign help for his presidential campaign. So did presidential candidate Richard Nixon. The difference, writes scholar Ken Hughes, is that Nixon was more skilled at it.
What is the 'Steinmeier formula' for eastern Ukraine and why is it so controversial?
Africa has already felt the effects of Donald Trump's climate change denialism. Recent events are also raising political issues of keen interest among the continent's democrats.
A little-known provision of the Constitution might allow Trump to be reelected president in 2020 even if he is removed from office through the impeachment process.
Last week the PM got himself caught up in a Trump-created political rally. Now he's on the spot over this (typical) Trump call.
In many instances, whistleblowers find the abusive power they have revealed turned against them, both ending their careers and harming their personal lives.
A former congressional staffer says withholding damning evidence from Congress and using civilians to carry out presidential or intelligence agency agendas links the Ukraine crisis to other scandals.
How Ukraine has reacted to controversy over a phone call between its President Volodymyr Zelenskiy and Donald Trump.
The Founders saw as a regular part of ensuring presidential accountability. A constitutional scholar offers a possible process for a rapid and smooth impeachment inquiry.
As the House mounts an impeachment investigation of President Trump, examples from Central and South America show that ousting an executive leader from office doesn't always have the intended effect.
The United States is exhibiting several of the signs that have historically resulted in uprisings and revolutions. Is another American revolution looming?
Whether successful or not – and most impeachments are not – the fallout for the Democrats and the US will be deep and enduring.
The conflict between Congress and President Trump over his dealings with Ukraine's president is just the latest version of a long-running struggle for power between the two branches of government.
While some have seen Mueller's testimony as a disappointment, Democrats may still initiate impeachment proceedings against Donald Trump in the House of Representatives.
To one scholar of the post-truth era, tuning in to Robert Mueller's testimony Wednesday was to hear a duel over the facts. Not what the facts imply – but what the facts are.
Those who want President Trump out of office should forget about the 25th Amendment; it won’t work as they hope or believe. The amendment is a complex law that – by design – is very hard to use.