The U.S. Supreme Court has dealt a blow to President Donald Trump's waning ambition to remain in the White House. On Tuesday, the court threw out Republican petition that sought to invalidate up to 2.5 million mail-in ballots in Pennsylvania. With the highest court refusing to block Pennsylvania's Trump's efforts to overturn the election has all but hit the dead end.

The petition was filed by U.S. congressman Mike Kelly and other Pennsylvania Republicans. Joe Biden's victory in Pennsylvania was decisive in this year's election along with those in Michigan, Wisconsin and Georgia. Trump had won Pennsylvania in 2016.

Though the Supreme Court has a 6-3 conservative majority, there were no noted dissents from any of the justices on the court, Reuters reported.

"This election is over. We must continue to stop this circus of 'lawsuits' and move forward," Pennsylvania Attorney General Josh Shapiro, said after the court verdict.

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President Donald Trump snaps at Reuters correspondent Jeff Mason after being interrupted during a White House press conference on Thursday. Twitter

The Supreme Court also must decide what to do with another election-related case brought on Tuesday. Republican-governed Texas, hoping to help Trump, mounted an unusual effort to overturn the election results in Pennsylvania and three other states - Georgia, Michigan and Wisconsin - by filing a lawsuit against them directly at the Supreme Court.

The Republican plaintiffs argued that the universal, "no-excuse" mail-in ballot program passed by the Republican-controlled Pennsylvania legislature in 2019, enabling voters to cast ballots by mail for any reason, violated the state's constitution.

Biden won Pennsylvania by 80,000 votes and received a much higher proportion of the mail-in votes than Trump. Many more people voted by mail this year because of health concerns prompted by the coronavirus pandemic as they sought to avoid crowds at polling places.

Ahead of the election, Trump urged his supporters not to vote by mail, making groundless claims that mail-in voting - a longstanding feature of American elections - was rife with fraud.

Vote counting in Pennsylvania.
For representational purposes only. Twitter

Pennsylvania said in a court filing that the Republican challengers were asking the justices to "undertake one of the most dramatic, disruptive invocations of judicial power" in U.S. history by nullifying a state's certification of its election results.

The state said most of what the challengers had sought was moot because the election results already were certified and what they were really wanted was for "the court overturn the results of the election."

Stream of Lawsuits in Key States

Pennsylvania's top court on Nov. 28 dismissed the challenge, saying that the lawsuit was not filed in a timely manner when the mail-in voting law was first enacted. It threw out a lower court ruling that had ordered the state not to certify the election pending a hearing.

Trump's campaign and his allies have lost in a stream of lawsuits in key states won by Biden, also including Georgia, Michigan, Wisconsin and others. Judges have rejected sweeping assertions of voting irregularities.

Biden has amassed 306 electoral votes - exceeding the necessary 270 - compared to 232 for Trump in the state-by-state Electoral College that determines the election's outcome, while also winning the national popular vote by more than 7 million votes.

Tuesday represents a "safe harbor" deadline set by an 1887 U.S. law for states to certify presidential election results. Meeting the deadline is not mandatory but provides assurance that a state's results will not be second-guessed by Congress.

After this deadline, Trump could still pursue lawsuits seeking to overturn Biden's victory but the effort would become even more difficult.