(Photo : Charles Dharapak-Pool/Getty Images) U.S. Vice President Joe Biden (C), Senate Minority Leader Mitch McConnell (R-KY) (L), Rep. Shelia Jackson Lee (D-TX) (R) and others arrive on Capitol Hill on February 12, 2013 in Washington, D.C.

Former vice president Joe Biden and Senate majority leader Mitch McConnell have a record of cutting deals together in the Senate, but many things have changed in the past few years.

When Biden bid farewell to the Senate four years ago, McConnell looked him in the eye and described him as a "real friend" and a "trusted partner," reported USA Today. 

Years earlier, they worked in brokering a major tax deal.

Biden, who has been declared the winner in the presidential race by national media, wanted to raise taxes on wealthy estates, but McConnell wanted to keep them low.

As two long-time figures in Washington, they found a halfway point: the vote count.

With the Bush tax cuts nearing expiration in December of 2010, McConnell called Biden to let him know that Republicans have enough votes to keep the tax lower. Biden respected the numbers.

Read also: US Election Explainer: What Happens Between Now and President-Elect Biden's Inauguration?

It was a point of agreement for both politicians. More than that, it was the first of several times Biden and McConnell reached a bipartisan deal to avert a looming fiscal cliff during former president Barack Obama's term.

After the tax deal was brokered, McConnell invited Biden to an event at the University of Louisville as a gesture of goodwill.

Biden said if the public wants to see if a Democrat and Republican can "really like each other," he and McConnell did.

Multiple lawmakers and aides described Biden and McConnell to have a "sincere, if professional, bond," said The Washington Post.

McConnell-Biden Friendship Could Go Down with Legislative Agenda

That friendship will be tested now that Biden might be the nation's 46th president.

As McConnell will still be part of the incoming Biden administration, he will be expected to pass Biden's legislative priorities, approve his cabinet members, and confirm his judicial appointments. But that doesn't sit well with many of Biden's liberal supporters.

The hope was to get a Democrat-controlled Senate that can pass their progressive agenda: undoing tax cuts for the wealthy, the Green New Deal, and government-sponsored healthcare.

GOP Senator Lindsey Graham also thinks these liberal priorities are practically "dead on arrival" in the Senate. But like McConnell, Graham considers himself a long-time friend of Biden.

He believes he can reach common ground with Biden on several matters like cabinet appointments and certain legislation.

"I will try to help where I can and oppose him where I must," he told reporters Friday. 

McConnell Declined to Congratulate Biden

As President Donald Trump refused to concede, leading Republicans declined to recognize Biden's win. They insist that the election was stolen from Trump even as party division became apparent to the public, noted the New York Times.

Read also: What Happens If Trump Refuses to Concede Defeat? 

Among these leading Republicans is McConnell, who, in a lengthy floor statement Monday, declined to extend his congratulations to Biden.

He still did not recognize Biden as president-elect and instead defended Trump's legal fight against ballot counts in key states, said The Hill.

"We have at least one or two states that are already on track for a recount and I believe the president may have legal challenges underway in at least five states," McConnell said.

He noted that Trump was "100 percent within his rights" to pursue legal action that challenges the election outcome. He also hammered Democrats for expecting the president to concede, as the New York Times reported.

The GOP leader reiterated his party's stance that all legal ballots have to be counted. The Republicans demanded a process that was "transparent or observable by all sides."