Pre-election hostilities between the White House and US Congress spiked Wednesday as the surprise appearance of Joe Biden's son -- in Republican crosshairs over his business interests -- triggered pandemonium on Capitol Hill, the same day lawmakers launched efforts to impeach the administration's immigration chief.
Republicans are racing to inflict damage on the Biden government ahead of November's presidential election, where their nominee is likely to be scandal-plagued former president Donald Trump.
One key target is Hunter Biden, who Republicans insist used his father to peddle influence, even if no evidence has been provided of crimes.
A Republican-led House committee hearing on whether Hunter Biden should be held in contempt for refusing an order to testify behind closed doors -- he instead offered to testify in public -- erupted in chaos when the president's son himself suddenly showed up and sat in the audience.
Fiery Republican Representative Nancy Mace called his appearance a "PR stunt" and said "I think Hunter Biden should be arrested right here, right now, and go straight to jail."
As the session unraveled into a series of shouting matches, Mace claimed that Hunter Biden "wasn't afraid to trade access to Joe Biden" but was "afraid" to comply with the subpoena ordering him to testify to the committee.
Democrats responded scornfully.
"He's here. He doesn’t seem to be too afraid," Representative Jared Moskowitz said, referring to the impassive Hunter Biden.
"The only people afraid to hear from the witness, with the American people watching, are my friends on the other side of the aisle," he added, rattling off a list of Republican officials who defied their own subpoenas to testify about the 2021 assault on the US Capitol by Trump supporters.
Biden and his lawyers then filed out of the hearing, followed by Republican jeers.
Hunter Biden's lawyer Abbe Lowell told a scrum of reporters outside that his client was the victim of a "political crusade."
- Border row -
Elsewhere in the Capitol, Republican lawmakers -- doubling down on endeavors to exploit the Biden administration's vulnerability on immigration -- launched efforts to oust Homeland Security Secretary Alejandro Mayorkas.
The Republican majority in the US House of Representatives accuses Mayorkas of being derelict in his duty to secure the border, where officials are struggling to control illegal migration.
A record 10,000 migrants were detained daily in December after crossing illegally from Mexico in what Republicans have termed a "humanitarian catastrophe."
To remove Mayorkas from office would require impeachment in the House, then conviction in the Senate, where Democrats hold a slight majority and will easily block the procedure.
However, the issue is increasingly fraught for the Biden administration and the Mayorkas hearings will give Republicans a platform to launch their attacks.
"Secretary Mayorkas's refusal to follow the law is sufficient grounds for impeachment proceedings," congressional Homeland Security Committee chairman Mark Green said in his opening remarks.
The Republican accused the secretary of whipping up an "intentional" crisis through "gross incompetence" and a "years-long pattern of refusing to enforce the laws passed by Congress."
A House floor vote to remove the homeland security secretary is expected as soon as late January and appears to have a good chance of passing, before going to the Senate.
The administration has dismissed the Mayorkas impeachment as a "baseless and pointless" political stunt while pointing out that its request for Congress for an extra $14 billion in border security funding has been stalled for months.