With all six states where Trump has contested election results now having certified Biden’s win -- with the battlegrounds of Arizona and Wisconsin making it official Monday, Trump is lashing out at Republican governors for certifying the votes in his ongoing effort to undermine the election.

Trump has targeted GOP Govs. Doug Ducey of Arizona and Brian Kemp of Georgia for meeting the deadlines to certify votes in their states, but as he publicly questions the credibility of the Republican Party and its leaders -- ahead of runoffs in Georgia that will determine control of the Senate -- some Republicans worry he is also undermining the GOP’s majority in the upper chamber.

Trump called on Kemp Tuesday morning in a tweet to "call off election," adding "it won't be needed," if Kemp allows his state to be "scammed" without checking signatures against ballots -- which the state already does. (Signatures were already matched twice in Georgia: first when a voter applies for a ballot and then again when the voter returned their absentee ballot. Once the signature accompanying the returned ballot is verified, the ballots are separated from the envelopes and there is no way to re-match them under the Georgia state Constitution.)

Near the end of an all-day unofficial "hearing" GOP lawmakers held at a hotel in Phoenix Monday, the president phoned in and called the election the "greatest scam ever perpetrated upon our country,” despite elected officials across the country praising the 2020 election as the most secure in American history.

"We're taking it all the way," Trump said, vowing his team would file additional legal action in Wisconsin -- where a recount netted Biden 87 more votes -- and Georgia -- where the Trump campaign has paid for votes to be counted for a third time.

Despite Trump’s unprecedented attacks on the electoral process, Biden is pressing forward with his transition with 50 days until the inauguration. He’s slated to introduce his incoming economic team Tuesday at 12:30 p.m. in Wilmington, Delaware, which includes former Federal Reserve Chair Janet Yellen as his Treasury secretary nominee who, if confirmed, would be the first woman in the position.

While Yellen has drawn bipartisan support in initial reactions on Capitol Hill, Biden’s nominee to lead the Office of Budget and Management, Neera Tanden, who would be the first woman of color and first South Asian American in the role, has drawn the ire of Senate Republicans with Texas Sen. John Cornyn calling her “radioactive.” Democrats have rallied to Tanden's defense.

Tuesday also brings the first time Biden will publicly appear in a walking boot after fracturing bones in his right foot over the weekend, and the second day he and Vice President-elect Kamala Harris will receive the latest intelligence in the President's Daily Brief, following a 16-day standoff with the Trump administration.

Following criticism from President Donald Trump on Monday, Gov. Doug Ducey defended Arizona's election system and its security, saying, "I’ve been pretty outspoken about Arizona’s election system, and bragged about it quite a bit, including in the Oval Office. And for good reason," he tweeted Monday night.

"We’ve been doing early voting since 1992. Arizona didn’t explore or experiment this year. We didn’t cancel election day voting as some pushed for — we weren’t going to disenfranchise any voter. In Arizona, we have some of the strongest election laws in the country, laws that prioritize accountability and clearly lay out procedures for conducting, canvassing, and even contesting the results of an election," Ducey continued.

Ducey, a Republican and ardent supporter of the president, directly responded to claims made Monday in the hearing that absentee and early ballots sent in Maricopa County did not undergo signature verification.

"We’ve got ID at the polls. We review EVERY signature (every single one) on early ballots — by hand — unlike other states that use computers. Prohibitions on ballot harvesting. Bipartisan poll observers. Clear deadlines, including no ballots allowed after Election Day," he said.

He broke down the state's law surrounding election certification and the selection of electors-- refuting claims from the Trump team and others asking state legislatures to bypass election results and select electors themselves.

"The problems that exist in other states simply don’t apply here. I’ve also said all along, I’m going to follow the law. So here’s what the law says… It requires the Secretary of State, in the presence of the Governor and the Attorney General, to canvass the election on the fourth Monday following the general election. That was today."
-ABC News' Meg Cunningham

Pennsylvania's legislative session officially ends at midnight, which means that state lawmakers are expected to adjourn without Republicans taking any action to replace the state's voter-awarded electors with a slate of ones chosen by the state's legislators.

Prior to Monday's deadline, the Republican Speaker of the Pennsylvania House of Representatives Bryan Cutler, along with Pennsylvania House Majority Leader Kerry Benninghoff issued a joint statement saying they did not have enough time to consider the resolution before the end of the session.

"We are physically unable to consider any new legislation before the end of session. A simple resolution takes three legislative days for consideration and a concurrent resolution takes five legislative days to move through both chambers, which means we do not have the time needed to address any new resolutions in our current session," the statement read.

However, the pair also indicated that this year's election would still be a topic that lawmakers plan to address in the future.

"It is obvious Pennsylvania's election processes are in dire need of repair. Our work to ensure the chaos and confusion of the 2020 election are not repeated will continue in the next legislative session," they added, while also noting that they plan to see the process of a "complete audit of the election...completed into the next session as well."

-ABC News' Alisa Wiersema and Alex Hosenball

The president called into a hearing underway at a hotel in Phoenix and called the election the "greatest scam ever perpetrated upon our country."

He claimed that he won Arizona, Michigan, Georgia, Pennsylvania and Wisconsin -- despite certified results. And though Trump said Monday that the election was "rigged," secretaries of state across the country, along with former CISA director Chris Krebs, have praised the security and success of this year's election.

On the call, Trump also said his team would be filing additional legal action in Wisconsin and Georgia.

"We're taking it all the way," Trump said.

-ABC News' Meg Cunningham