The outcome of Tuesday’s Georgia Senate runoff elections will shape Joe Biden’s presidency even before it officially begins on Jan. 20, setting the scope of his agenda and the pace of his nominees’ confirmations -- and previewing whether Republicans can launch robust investigations into him and his family. Biden won the November election with bold pledges to amplify the federal response to the coronavirus pandemic, release billions more in economic stimulus and raise taxes on corporations and people who make more than $400,000 a year. Those and many others will require legislation. If Democrats Jon Ossoff and Raphael Warnock both win, the Senate will be divided 50-50 between the parties and Vice President-elect Kamala Harris can cast a tie-breaking vote to help advance that agenda. If Republicans David Perdue or Kelly Loeffler win one of the seats, Republicans will have 51 votes -- enough to block any Biden initiative, from approving his cabinet onward. “I don’t think it’s possible to overstate it,” said Casey Dominguez, a political scientist at the University of San Diego. “Who gets the majority leader’s office in the Senate is incredibly important.” Without those two Senate seats, Biden would be the first chief executive to begin his presidency under divided government since George H.W. Bush in 1989. In the 32 years since, Washington has only gotten more partisan, and significant factions of the Republican Party have refused to acknowledge Biden’s very legitimacy as president. Perdue underscored the dramatic stakes when he called in to Vice President Mike Pence’s rally in Georgia on Monday from where he was quarantining after exposure to Covid-19. “The very future of our republic is on the line,” he said, echoing the sentiments of the other candidates. “This will determine the future of America for a long, long time.” On Monday night, he made a similar appeal on video to a rally in Dalton led by President Donald Trump, who invited Loeffler to address the crowd. Even if Democrats win that barely-there majority, it may not be enough to result in a blitz of Biden-backed bills, thanks to the Senate filibuster, which requires 60 votes to cut off debate and pass a piece of legislation. But once a year, the Senate can pass a taxing and spending bill with a simple majority vote under a process known as budget reconciliation. That’s how President Bill Clinton got a welfare overhaul in 1996, how President Barack Obama adopted the Affordable Care Act in 2010 and how President Donald Trump enacted his signature tax cuts in 2017. Biden could pass major stimulus legislation the same way. Because Congress never adopted a budget for the current fiscal year, Biden could use the procedure twice in the coming months creating fiscal 2021 and 2022 reconciliation bills. Democrats, with a majority, would also face pressure from the left to dismantle the filibuster and deny Republican senators the chance to influence legislation. Biden, a senator from Delaware for 36 years, has supported the filibuster in the past. But he said last year he would be willing to reconsider, depending on how “obstreperous” Republicans are in blocking his agenda. And the messy post-election period, with a dozen senators and more than 100 House Republicans challenging Biden’s legitimacy, makes it less likely he will maintain his long-standing position. That could open the door to even more far-reaching legislation. Some Democrats have advocated increasing the size of the Supreme Court, giving Biden a chance to fill some lifetime seats. He has proposed an 18-month bipartisan commission to study the issue. A Republican Senate would mean Biden would have to make good on his campaign promise to find common ground. But a chamber led by Mitch McConnell would likely preclude any action on taxes, immigration or climate -- areas where the ideological distance between the parties is greatest. He might find Republicans willing to work with him on issues like infrastructure spending and cybersecurity. Subscribe to our YouTube channel: https://bit.ly/2TwO8Gm Bloomberg Quicktake brings you live global news and original shows spanning business, technology, politics and culture. Make sense of the stories changing your business and your world. To watch complete coverage on Bloomberg Quicktake 24/7, visit http://www.bloomberg.com/qt/live, or watch on Apple TV, Roku, Samsung Smart TV, Fire TV and Android TV on the Bloomberg app. Have a story to tell? Fill out this survey for a chance to have it featured on Bloomberg Quicktake: https://cor.us/surveys/27AF30 Connect with us on… YouTube: https://www.youtube.com/user/Bloomberg Breaking News on YouTube: https://www.youtube.com/c/BloombergQuickTakeNews Twitter: https://twitter.com/quicktake Facebook: https://www.facebook.com/quicktake Instagram: https://www.instagram.com/quicktake