By Patricia Zengerle and Richard Cowan

WASHINGTON (Reuters) -President Donald Trump’s extraordinary bid to undo President-elect Joe Biden’s election victory goes before a marathon joint session of the U.S. Congress on Wednesday in a showdown led by a band of Republican lawmakers that is almost certain to fail.

The Republican-led Senate and Democratic-controlled House of Representatives were due to meet to formally certify the results of the Nov. 3 election in proceedings that could stretch past midnight.

Although Biden, a Democrat, won the election by a 306-232 count in the state-by-state Electoral College and by a margin of more than 7 million ballots in the national popular vote, the Republican president has falsely claimed there was widespread fraud and that he was the victor. Trump’s allies plan to challenge the results from a handful of states won by Biden.

State and federal reviews have debunked Trump’s claims of massive election fraud even as increasingly desperate legal efforts by his campaign and allies on the right to overturn the election have failed in numerous courts all the way up to the U.S. Supreme Court.

Biden is due to take office on Jan. 20.

Despite pressure from Trump to help overturn his election loss, Vice President Mike Pence, set to preside over the proceedings, will stick to his ceremonial duties and not block the congressional certification of Biden’s victory, advisers said. Pence, a loyal lieutenant during the four years of Trump’s tumultuous presidency, has no plans to intervene and has told Trump he lacks the power to do so, they said.

Trump took to Twitter to again make unfounded claims of election irregularities, writing, “Our Election Process is worse than that of third world countries!”

“BE STRONG!” he added.

Senator Ted Cruz, seen as a potential 2024 presidential candidate, is expected on Wednesday afternoon to lead at least 11 other Republican senators, alongside a majority of the 211 Republicans in the House of Representatives, in objecting to Electoral College results being formally approved by the two chambers of Congress: the Senate and the House of Representatives.

Under the U.S. Constitution, a presidential election is determined not by the national popular vote but in the Electoral College, with states allotted votes partly based on their populations. The states already have certified their results and Biden was affirmed as the Electoral College winner last month.

DRAMA IN CONGRESS

The proceedings scheduled to begin at 1 p.m. EST (1800 GMT) for Congress to formally certify the presidential election results, the final step in a monthslong process, normally would be ceremonial and perfunctory. But Trump and his allies have seized upon them in a last-ditch bid to reverse the results of a democratic election deemed by state and federal experts to have been free and fair.

This year, the proceedings could drag into Thursday.

Critics of Trump and his allies have painted the efforts to try to reverse the election in Congress as an attack on democracy and the rule of law and an attempted legislative coup.

Cruz is bucking Senate Majority Leader Mitch McConnell, who has recognized Biden’s victory and urged his fellow Republicans not to pursue the challenges, which appear to lack the political support they would need to succeed.

Republican senators, including Josh Hawley and James Lankford, have joined forces with Cruz, while other prominent members of the party, including Senator Mitt Romney and Representative Liz Cheney, oppose it.

Supporters of Trump gathered in Washington for protests as they take up the president’s unfounded claim that the election was stolen from him in an elaborate conspiracy. Trump had urged supporters, who include the violent Proud Boys, to take to the streets.

Trump will speak to protesters on a grassy expanse known as the Ellipse near the White House, according to a person briefed on his plans, and on Twitter he has said the demonstrations “will be wild.”

November and December protests involving the Proud Boys were marred by some stabbings and brawls. Police have arrested the group’s leader on charges of destruction of property related to an earlier protest and possession of a firearms magazine.

Many Republican senators who have refused to challenge the election results have received death threats on their office voice mail, a senior Senate Republican aide said.

STATE BY STATE

The Electoral College results will be presented alphabetically, starting with Alabama. Republicans are expected to challenge results in Arizona, Michigan, Wisconsin, Georgia, Pennsylvania and Nevada.

If the challenges are ultimately defeated as anticipated, Pence, acting in his role as president of the Senate, is expected to proclaim Biden the next president and Senator Kamala Harris as the next vice president.

The U.S. Constitution does not give Pence the power to unilaterally overturn the results of the election but he is under pressure to do so from Trump.

“The Vice President has the power to reject fraudulently chosen electors,” Trump wrote on Twitter on Tuesday.

If at least one House member and one Senate member object to a state result, each chamber would hold separate debates for each of those states lasting up to two hours. Each chamber would then vote to accept or reject the challenge and then report the result to the joint session of Congress, before moving onto the next challenge.

In the Democratic-led House, Speaker Nancy Pelosi will preside, a senior Democratic aide said. While Pence is due to preside over the joint session, he might allow senior Republican Senator Chuck Grassley to preside over the Senate debate.

In registering his objection, Cruz is expected to call for the creation of an emergency election commission to look into voting irregularities claimed by Trump’s allies, a source familiar with the upcoming deliberations said.

The Republican maneuvering has created fissures within Trump’s party and among outside groups normally supportive of it. Senator James Inhofe said challenging a state’s election certification would be “a violation of my oath of office.” Senator Rob Portman said that after two months of recounts and legal challenges, there has been no evidence of fraud or irregularities widespread enough to change the election results.

(Reporting by Richard Cowan and Susan Cornwell; Writing by Will Dunham; Editing by Scott Malone, Sonya Hepinstall and Jonathan Oatis)