Hawley joins some of President Donald Trump's staunchest Republican allies on Capitol Hill on what could be one of the president's last attempts to challenge the certification of the presidential election results in January and disrupt the peaceful transfer of power to President-elect Joe Biden.
Hawley alleges that some states failed to follow their election laws and that Big Tech interfered on behalf of Biden.
He's the first Republican senator joining a group of House members who also plan to object to the Electoral College results, in what is expected to be a symbolic political stand, delaying the certification of the presidential race results by hours, rather than alter the results.
“I cannot vote to certify the electoral college results on January 6 without raising the fact that some states, particularly Pennsylvania, failed to follow their own state election laws. And I cannot vote to certify without pointing out the unprecedented effort of mega corporations, including Facebook and Twitter, to interfere in this election, in support of Joe Biden,” Hawley noted in a statement. “At the very least, Congress should investigate allegations of voter fraud and adopt measures to secure the integrity of our elections. But Congress has so far failed to act. For these reasons, I will follow the same practice Democrat members of Congress have in years past and object during the certification process on January 6 to raise these critical issues."
Under federal law, a member of the House or Senate can contest the Electoral College results from any state, separating the House and Senate for up to two hours of debate before a vote on whether to accept a slate of electors.
Majorities in both chambers would need to support the motion to successfully challenge a given slate of electors, according to the Congressional Research Service.
The vote could put other Senate Republicans in a tough position, as Hawley's move will compel his colleagues in the GOP conference to vote on the record on whether they agree with President Trump's allegations of widespread election and voter fraud.
Prior to Hawley’s move, Sen. John Thune, the Senate Majority Whip, predicted Senate Republicans could defeat any general effort to challenge the electoral results.
"The thing they've got to remember is, it's just not going anywhere. In the Senate it will going down like a shot dog," Thune said.
Trump's efforts to cast doubt on the results of the election by alleging widespread fraud have been undercut by state leaders, election officials, courts across the country including the Supreme Court, an agency that led the Department of Homeland Security's efforts to secure the election, and his former chief law enforcement officer. In an interview with The Associated Press prior to resigning, then-Attorney General Bill Barr acknowledged that the Justice Department has uncovered no evidence of widespread voter fraud that would change the outcome of the election.
The House and Senate last debated the certification of electors in 2005, when Sen. Barbara Boxer, D-Calif., and the late Rep. Stephanie Tubbs Jones, D-Ohio, pushed their own challenge over concerns about voting procedures in Ohio that fall. That effort, however, was not aimed at overturning the results of the election, Boxer said at the time. In 2017, then-Vice President Joe Biden, presiding over the joint session of Congress, dismissed a challenge from House Democrats because it lacked Senate support.
On Wednesday, House Speaker Nancy Pelosi also dismissed Hawley's move, predicting Biden will prevail over any attempt for Trump to remain in office.
“I have no doubt that on next Wednesday, a week from today, that Joe Biden will be confirmed by the acceptance of the vote of the Electoral College as the 46th President of the United States,” she said.
ABC News' Ben Siegel, Mariam Khan and Kendall Karson contributed to this report.