Republicans prepared Wednesday to launch efforts to impeach Joe Biden's immigration chief and target the US president's son for prosecution, in a major escalation of election-year hostilities with the White House.
Party strategists see the maneuvers as key to inflicting damage on the Democratic administration ahead of November's presidential election, as they circle the wagons around their own likely nominee, the scandal-plagued Donald Trump.
Hunter Biden is in the crosshairs for defying a subpoena to testify to Congress about his business interests, while conservatives are pushing to oust Homeland Security Secretary Alejandro Mayorkas in a row over border security.
"The legislative branch writes the laws and the executive branch executes those laws. They don't get to pick and choose which laws," senior Republican Mark Green told Fox News.
"And clearly Secretary Mayorkas has basically forced his immigration policy on the country against the laws passed by Congress."
The Republican majority in the US House of Representatives accuses Mayorkas of being derelict in his duty to secure the border, which has seen record numbers of illegal crossings in recent weeks.
Impeachment by the House would set up a trial in the Senate, with Mayorkas's job on the line -- but it is largely seen as a symbolic move as the Democratic-led upper chamber of Congress is almost certain to acquit.
A record 10,000 migrants were detained daily in December after crossing illegally from Mexico in what Republicans have termed a "humanitarian catastrophe."
The House Homeland Security Committee holds an initial Mayorkas hearing at 10:00 am (1500 GMT), focusing on how the influx has impacted Midwestern states, with further action yet to be announced.
Witnesses include the attorneys general of Missouri, Montana and Oklahoma, who joined a court filing backed by 23 states last year in support of a successful lawsuit filed by Florida to end "catch and release" asylum policies.
Lawmakers will also hear from University of Missouri law professor Frank Bowman, who wrote an article last March calling the effort to impeach Mayorkas "bunk."
A House floor vote to remove the homeland security secretary, a member of Biden's cabinet, is expected as soon as late January and appears to have a good chance of passing, with Republicans backing the effort and Democrats in vulnerable districts wary of intervening.
The administration has dismissed the Mayorkas impeachment as a baseless political stunt while pointing out that its request for Congress for an extra $14 billion in border security funding has been stalled for months.
House Republicans have also launched an impeachment investigation into Biden over allegations -- for which they have provided no evidence -- that the president benefited from his son Hunter's foreign business dealings.
The younger Biden rebuffed a congressional subpoena issued in November demanding his testimony behind closed doors, pressing instead to go straight to a public hearing.
House Republicans -- several of whom defied their own subpoenas to testify about the 2021 assault on the US Capitol by Trump supporters -- released a resolution this week to hold the younger Biden in contempt of Congress.
"Mr. Biden's willful refusal to comply with the committees' subpoenas constitutes contempt of Congress and warrants referral to the appropriate United States Attorney's Office for prosecution as prescribed by law," the accompanying report read.
As the Mayorkas hearing gets underway, the House Oversight and Judiciary committees will both meet to approve the resolution for a vote of the full House, expected as soon as this week.
The president's son is due to appear in a Los Angeles court on Thursday to answer federal charges that he failed to pay taxes on millions of dollars he received from foreign businesses.
It is the second time this year he has faced charges from a special counsel investigating his personal and business dealings.
