US Democrat Nancy Pelosi Tuesday announced the opening of a formal impeachment inquiry into President Donald Trump, saying he betrayed his oath of office by seeking help from a foreign power to hurt his Democratic rival Joe Biden.
The dramatic move, the first step in a complex process that stands little chance of driving Trump from office, pushed US politics into a perilous new chapter just 14 months before new elections for control of the White House and Congress.
Trump has denounced the inquiry as "Witch Hunt garbage" -- while also claiming it would help his re-election chances in 2020.
"The actions of the Trump presidency revealed the dishonorable facts of the president's betrayal of his oath of office, betrayal of our national security, and betrayal of the integrity of our elections," Pelosi told a news conference in the US capital.
"Therefore, today I'm announcing the House of Representatives moving forward with an official impeachment inquiry."
'No one is above the law'
Pelosi, the speaker of the House of Representatives, and other Democratic Party leaders had resisted taking the step for months, preferring to focus on the coming election fight.
But a combination of the newest allegations that Trump offered Ukraine aid in return for help to damage Democratic White House frontrunner Biden, and a groundswell of support for impeachment among the party's rank and file, appeared to tip the balance.
"The president must be held accountable. No one is above the law," she said.
Now that a formal inquiry has been made, a committee would normally be assigned the task of gathering evidence to support the case against the president.
If the evidence is firm enough, the committee will draft articles of impeachment -- formal charges against the president -- for the entire House to vote on. They can pass with a simple majority.
From there the process would go to the Senate, where the Republican majority could conceivably block a formal trial of the president. If a trial is held, conviction would require two-thirds of the Senate to vote in support, leading to the president's removal.