Democratic nominee Joe Biden was on the brink of securing the 270 electoral votes needed to win the presidency Saturday as he increased his lead in Pennsylvania and other key battleground states -- while President Trump forged ahead with a legal fight.

As of Saturday morning, Biden led Trump by less than 29,000 votes in Pennsylvania with roughly 90,000 ballots still to count. The Keystone State's 20 electoral votes would give Biden the victory. 

The race is also tight in Arizona, Georgia and Nevada, where Biden also led early Saturday. Trump was ahead in Alaska and North Carolina, the only other states that have not yet been called.

BIDEN CLAIMS 'MANDATE' WHILE ELECTION VS TRUMP REMAINS UNDECIDED 

Pennsylvania has been the target of a legal challenge by the Trump campaign over the counting of ballots, with the campaign alleging fraud while objecting to the counting of votes received after 8 p.m. on Election Day.

“Tens of thousands of votes were illegally received after 8 P.M. on Tuesday, Election Day, totally and easily changing the results in Pennsylvania and certain other razor thin states,” Trump tweeted Saturday.

On Friday evening, Supreme Court Justice Samuel Alito reaffirmed in a ruling that late mail-in ballots, those that arrived after 8 p.m. ET Tuesday and before Friday at 5 p.m. ET, need to be segregated and counted separately as part of such a challenge. Those ballots are currently being included in the count.

Trump and his campaign have alleged there have been other fraud and “shenanigans” connected to the counting of ballots -- flagging the surge in votes that Biden has received from mail-in ballots after the election. The Trump campaign has been fighting for, and eventually secured, closer access to the count for observers in Philadelphia.

SEE THE VOTE: AS IT STANDS 

However, the campaign has  yet to produce evidence of a massive voter fraud operation by Democrats. Lawsuits make such allegations have been thrown out by judges in a number of swing states.

Meanwhile, Biden’s lead in several crucial states was slowly growing.

In Nevada, the advantage for Biden was 22,657 votes. His lead in Georgia was a razor-thin 7,245 and heading toward a recount. Trump, meanwhile, continues to lead by a narrow margin in North Carolina.

As Trump vows to fight on, Biden is preparing to claim victory and start addressing the challenges facing the nation.

"We don’t have a final declaration of victory yet but the numbers tell us a clear and convincing story. We’re going to win this race," Biden said Friday night in Wilmington, Del.

Biden said a "record number of Americans of all races, faiths, religions, chose change over more of the same. They’ve given us a mandate for action on COVID, the economy, climate change, systemic racism. They’ve made it clear they want the country to come together."

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However, should Biden win the presidency, his ability to pass parts of a progressive agenda could be limited. Republicans appear likely to keep control of the Senate -- although that will not be known until the results of two Senate runoffs in Georgia slated for early January.

Meanwhile, House Speaker Nancy Pelosi’s majority in the House was being cut into by Republicans -- leading to finger-pointing between progressives and moderates about who is to blame.