Explainer-Why Republicans impeached Biden's top border official Alejandro Mayorkas

By Ted Hesson

WASHINGTON (Reuters) - The Republican-controlled U.S. House of Representatives this week is due to deliver its impeachment case against President Joe Biden's top border official, Homeland Security Secretary Alejandro Mayorkas, to the Democratic-majority Senate.

That chamber's majority Democrats are seen as all but certain to bring the proceedings to a swift end, arguing that Republicans have fallen short of the "high crimes and misdemeanors" standard that impeachment calls for.

WHY DID HOUSE REPUBLICANS IMPEACH MAYORKAS?

Republicans accuse Biden and Mayorkas of failing to sufficiently deter illegal immigration across the U.S.-Mexico border, which has reached record levels since the Democratic president took office in 2021.

Republicans argue that Mayorkas refused to fully enforce U.S. immigration laws and should not have reversed restrictive policies put in place by Republican former President Donald Trump, Biden's leading rival in the Nov. 5 election.

Republicans also contend Mayorkas exceeded his authority by allowing hundreds of thousands of migrants to enter legally through emergency "parole" programs.

The U.S. Border Patrol made more than 1 million arrests of migrants crossing the U.S.-Mexico border illegally in the past six months, according to internal agency statistics reviewed by Reuters, a pace similar to record-breaking totals during Biden's first three years in office.

During Trump's 2017-2021 presidency, migrant arrests peaked at 852,000 in fiscal year 2019.

Reuters/Ipsos polling shows that immigration is the top concern for Republicans and the party has used the issue to motivate their base.

HOW HAVE DEMOCRATS RESPONDED TO REPUBLICAN ATTACKS?

The Biden administration says it has created a more orderly and humane immigration system and that record levels of migration are challenging countries throughout the Western Hemisphere.

In recent months, Biden has toughened his border rhetoric and tried to shift blame to Republicans for high levels of illegal crossings.

Specifically, the president has faulted Republicans for declining to provide more funding for border enforcement and for rejecting a bipartisan border deal in the Senate that would have given Biden a sweeping authority to send migrants caught at the southwest border back to Mexico. Trump voiced loud objections to the bill, dooming its chances in the House.

Mayorkas - a former federal prosecutor - defended his immigration enforcement record and commitment to government service in a January letter to House Homeland Security Committee Chairman Mark Green.

Representative Bennie Thompson, the top Democrat on the homeland committee, has dismissed the impeachment proceedings as a politically motivated "sham."

ARE THERE GROUNDS FOR IMPEACHMENT?

Several constitutional experts have said the allegations against Mayorkas raised by Republicans do not meet the high bar for impeachment outlined in the U.S. Constitution.

The only Cabinet member ever to be impeached by the House was former President Ulysses S. Grant's secretary of war, William Belknap in 1876 following allegations of corruption. He was acquitted by the Senate.

Frank Bowman, a University of Missouri law school professor and impeachment expert, said at a January hearing that Republicans had not provided evidence that Mayorkas had committed potentially impeachable actions such as corruption, abuse of power or subversion of the U.S. Constitution.

"Whatever may be the grounds for impeachment and removal, dislike of a president's policy is certainly not one of them," Bowman said, quoting the late constitutional scholar Charles Black.

Other scholars have raised concerns that Republicans have weaponized impeachment for political gain, setting a dangerous precedent for the divided U.S. government. Hardline Republican Representative Marjorie Taylor Greene began to push for Biden's impeachment immediately after he took office in January 2021, a move that observers described as revenge for House Democrats twice impeaching Trump, a historic first. Both times Trump was acquitted by the Senate.

Republicans also have launched an inquiry into whether Biden improperly benefited from his son Hunter Biden's foreign business dealings.

WHAT WILL HAPPEN IN THE SENATE?

The Republican-controlled House impeached Mayorkas on its second attempt on Feb. 13, with a 214-213 vote that fell almost entirely along party lines. The impeachment followed a failed vote a week earlier.

Mayorkas is unlikely to be convicted of the charges in the Senate, where Democrats hold a 51-49 majority.

WHAT DO REPUBLICANS WANT AT THE BORDER?

Republican House Speaker Mike Johnson has said Biden needs to reinstate Trump policies and crack down on border crossings.

Johnson also has called on the Senate to approve a bill passed by the House in May 2023 that would effectively end access to asylum at the border.

The measure, known as H.R. 2, passed with broad Republican support but with no backing from Democrats.

The bill has not come to a vote in the Senate, where it would face steep Democratic opposition. Even if it passed the Senate, the White House has said Biden would veto it.

The bill generally bars migrants from seeking U.S. asylum at the border if they passed through another country en route to the United States, one of several provisions that would greatly reduce such claims for protection.

The legislation grants the U.S. homeland security secretary sweeping authority to suspend entry to migrants to maintain "operational control" of the border, a standard defined as prevention of all illegal entries.

Johnson rejected the bipartisan bill brokered in the Senate, saying it would not adequately reduce illegal crossings and would be "dead on arrival" in the House.

(Reporting by Ted Hesson in Washington; Editing by Scott Malone and Alistair Bell)