As promised, Joe Biden has launched his fledgling administration with a flurry of activity. In his first two days, the President signed 30 executive actions addressing his priorities on climate change, immigration, the COVID-19 pandemic, and more.

But executive orders will only get the Biden administration so far in pursuing its expansive agenda; for the rest, it will require the cooperation of a U.S. Congress still coming to terms with its recalibrated power dynamics. Though Democrats now control both chambers after winning back the Senate in a stunning upset, the Republican minority led by Sen. Mitch McConnell (R-Ky.) is still jostling for position, and it’s clear that the President’s party has its work cut out in passing all the things on its docket.

McConnell is already angling to preserve the Senate filibuster that effectively requires that most legislation be passed by a 60-vote majority, as he and Senate Majority Leader Chuck Schumer (D-N.Y.) negotiate a power-sharing agreement for a closely divided body. Senate Democrats have urged Schumer to hold a strong line, arguing against ceding a valuable bargaining chip against the opposition’s obstructionist designs.

Should filibuster rules remain intact, Democrats may have to resort to more creative tactics to advance parts of Biden’s agenda. Most notably, there is the $1.9 trillion coronavirus relief package proposed by the President, which would bolster the federal response to the pandemic and provide needed economic relief to millions of Americans. While Democrats say they would prefer to work with Republicans on a bipartisan bill, they could rely on budget reconciliation measures to push through the legislation with a simple majority.

Both the White House and leading Senate Democrats have hinted at that tactic as a possible avenue. While noting the President’s “clear preference” for a bipartisan bill, Biden press secretary Jen Psaki said last week that the administration would not “take any tools off the table.” Incoming Senate Budget Committee chair Bernie Sanders (I-Vt.) was more forthcoming, saying that Democrats would have to “go forward with reconciliation” if necessary.

Passing other parts of the President’s agenda could prove even more difficult, though that’s not stopping Biden from rolling out ambitious proposals. On his first day in office, he announced a sweeping immigration bill that would overhaul the U.S. immigration system and provide a pathway to citizenship for 11 million undocumented residents—a plan that is already facing backlash from GOP lawmakers. A significant infrastructure package, with clean energy initiatives potentially folded in, is also understood to be a priority for the new administration. Absent bipartisan cooperation, Democrats could resort to budget reconciliation to pass elements of those proposals—though it would be far from the comprehensive reform being pitched by the White House.

Meanwhile, the Senate also has on its plate the not-insignificant task of confirming more than 30 of Biden’s cabinet nominees who lay in waiting. And hanging over it all remains the matter of Donald Trump’s second impeachment trial; after McConnell on January 21 suggested pushing back the Senate trial to February, House Speaker Nancy Pelosi (D-Calif.) said on January 22 that she would send the article of impeachment against the former President to the upper chamber on January 25—triggering the start of the trial at an already busy time for the Senate.

In a television interview on January 21 night, White House chief of staff Ron Klain urged Congress to press forward with its duties, citing the need to fund the administration’s pandemic response and aid millions of Americans who are struggling economically.

“We’d like Congress to act as quickly as possible,” Klain said. “Sen. Schumer has made it clear he’s going to make sure that the Senate does all of its business.”