The unexpected new balance of power giving Democrats only the barest control of Congress has big consequences for next president - easy confirmation of his Cabinet most importantly - but the road ahead for the next US president's ambitious legislative agenda remains complicated and murky.
Republicans remain poised to block most of Joe Biden's proposals, just as they thwarted much of President Barack Obama's efforts on Capitol Hill. But 50/50 control permits action on special legislation that can't be filibustered, and momentum for the popular parts of Covid-19 relief could easily propel an early aid bill into law.
What 50-50 really gets - and doesn't get - Biden as he takes office:
What Biden does get?
With Democrats chairing committees in the Senate and only needing a majority to win floor votes on nominations, Biden is now assured of sealing confirmation of his Cabinet and judicial picks - including potentially for the Supreme Court. It also means controversial choices such as Neera Tanden, Biden's pick for budget director, can look ahead to assuming their posts. Republicans can slow but not stop nominations.
Democrats also have the opportunity to pass special budget-related legislation by a simple majority, an often-arcane process that enabled Obama to finish his 2010 health care bill and gave President Donald Trump's Republican allies a failed chance to repeal "Obamacare" and passage of a tax overhaul bill. Biden could use this so-called budget reconciliation process to pass more controversial elements of Covid-19 relief with only Democratic votes, repeal some of Trump's tax cuts or make federal health care programmes more generous, for example.