By Jan Wolfe and Lawrence Hurley
WASHINGTON (Reuters) - The Supreme Court's deadlock this week in a key election case illustrates the power President Donald Trump's nominee Amy Coney Barrett could wield and reveals why Republicans are hurrying to install her as a justice, Democrats said on Wednesday in their latest pitch to block her U.S. Senate confirmation.
Chief Justice John Roberts broke with the four other conservative justices and joined with the court's three liberals on Monday in denying a request by Republicans seeking to block a state court's ruling that extended the deadline for the delivery of mail-in ballots in Pennsylvania by three days.
That produced a 4-4 vote on the court - down a justice following the September death of liberal Ruth Bader Ginsburg - yielding a deadlock that preserved the lower court's ruling.
There has been an upswing in voting by mail due to the coronavirus pandemic. Democrats said that if Barrett already were on the court she would have voted in favor of the Republican bid to block the extension in Pennsylvania, a state crucial to Trump's re-election chances.
The Pennsylvania case, Democratic Senator Dick Durbin said during a call with reporters, "was a disturbing demonstration of what's at stake if the Republicans have their way and fill this vacancy."
"With one more vote they would have succeeded," Durbin said. "That's exactly the kind of judicial activism Republicans claim to oppose. ... It's exactly the kind of judicial activism they are expecting from Judge Barrett as they rush to confirm her."
Trump has asked the Republican-led Senate to confirm Barrett before Election Day, saying he expects the Supreme Court to decide the outcome of his race against Democratic challenger Joe Biden, who leads in national opinion polls even as Trump seeks to sow doubts about the integrity of the voting process.
Barrett's confirmation would give the court a 6-3 conservative majority and curb Roberts' current role as its swing vote in close cases.
Pennsylvania Republicans had argued that the state Supreme Court had overstepped its authority in extending a deadline that should be left to the legislature. The Supreme Court's four most conservative justices, including Trump's two previous appointees Neil Gorsuch and Brett Kavanaugh, said they would have granted the Republican request.
The Senate Judiciary Committee held Barrett's confirmation hearing last week and is expected to vote on Thursday to send her nomination to the full Senate for final approval next Monday. Republicans hold a 53-47 Senate majority, meaning Democrats have scant chance to halt her confirmation.
Democratic Senator Patrick Leahy said Trump sees Barrett as election insurance, saying, "He wants her to side with him when he makes his usual baseless claims of mail-in voting fraud. He wants a ninth justice to hand him the election."
"When you look at what's going on," added Democratic Senator Amy Klobuchar, "there are just cases all over the country and the Supreme Court, in so many of those cases, could end up being the final arbiter."
The Supreme Court only once has decided a presidential race. In 2000, its conservative majority clinched Republican George W. Bush's victory over Democrat Al Gore with a 5-4 decision involving ballots in Florida.
During her confirmation hearing, Barrett said she would not be beholden to Trump in any election case.
"I certainly hope that all members of the committee have more confidence in my integrity than to think that I would allow myself to be used as a pawn to decide this election for the American people," Barrett said, though she rebuffed Democratic pleas that she commit to recusing herself in such cases.
The Supreme Court may steer clear of a big election case this year, said Florida State University election law professor Michael Morley, noting an eagerness by Roberts not to thrust the justices into such disputes.
"I think this court is particularly aware of the judicial role and the desire to have the election decided by the people," Morley added.
But Roberts has only a limited ability to steer the court clear of a big election case like the one in 2000, Stetson University election law professor Ciara Torres-Spelliscy said.
"You are likely to have a conservative majority that can do whatever they want," Torres-Spelliscy added. "Chief Justice Roberts can't control five justices who are to the right of him."
(Reporting by Jan Wolfe and Lawrence Hurley; Editing by Scott Malone and Will Dunham)