U.S. Democrats secured unified control of the White House and Congress on Wednesday with the inauguration of President Joe Biden followed by Vice President Kamala Harris swearing in three new Democratic senators.

The three new senators bring the U.S. Senate to a 50-50 Democratic-Republican tie, with Harris as the presiding officer representing the tie-breaking vote.

With the U.S. House continuing under the leadership of Democratic House Speaker Nancy Pelosi, Biden begins his term with the opportunity to work with the two Democrat-controlled chambers to enact significant legislative changes. 

As a result of the shifting political power on Capitol Hill, Senate Democratic leader Chuck Schumer of New York has succeeded Republican Mitch McConnell as Senate majority leader. The Kentucky senator, who served in the top leadership post for six years, was highly skilled at blocking Democratic legislation, as well as advancing former President Donald Trump's judicial and administration nominees through the confirmation process. 

On the first full day of the Democratic majority in the Senate, Majority Leader Chuck Schumer, D-N.Y., left, is joined by Sen. Raphael Warnock, D-Ga., center, and Sen. Jon Ossoff, D-Ga., during a press event at the Capitol, Jan. 21, 2021.

With Republicans no longer in Senate leadership and chairing key committees, Biden is in a stronger position to pursue legislative action on his campaign promises to act on coronavirus aid, climate change, racial inequality and international relations. However, he cannot be assured that all Democrats will support him on every issue, and Republicans will be able to block some bills that require 60 votes for passage in the Senate.

Schumer acknowledged some of those challenges Wednesday in his first speech as majority leader.

"This Senate will tackle the perils of the moment: a once-in-a-generation health and economic crisis. And it will strive to make progress on generations-long struggle for racial justice, economic justice, equality of opportunity and equality under the law," Schumer said.

In the House, Pelosi was reelected as speaker despite losing Democratic seats in the November 2020 election. She can now afford to lose only a few votes from within her party and still pass legislation. Facing calls from the left wing of her party to enact progressive policies, Pelosi acknowledged Thursday there also could be opportunities to move to the center to work with Republican House members.

U.S. Speaker of the House Nancy Pelosi, Democrat of California, speaks during her weekly press briefing on Capitol Hill in Washington, Jan. 21, 2021.

"We have a responsibility to find bipartisanship where we can, to find that common ground," Pelosi told reporters Thursday.

Even with a narrow margin in the Senate and a diminished number of seats in the House, control of both chambers does clear a path for Biden to pass legislation, according to Casey Burgat, the director of the legislative affairs program at the George Washington School of Political Management. He says this is key for the Biden administration.

"Knowing that the president is of the same party, they know that anything that comes out of Congress is likely to get his signature on the bill instead of having a back and forth about a veto," he said. "So, it basically comes with unity and agenda control."

Biden said Thursday he would move quickly to send Congress a new proposal for coronavirus aid that likely would deliver a new round of stimulus checks to millions of Americans while funding a comprehensive vaccine distribution plan. Similar Democrat plans have languished for months, passing out of the House but failing to garner enough votes in the then-Republican-controlled Senate.

The schedule for Biden's Cabinet nominees also languished in the Senate in early January. With Democrats now in control of key committees, the pace of confirmations will accelerate considerably.

FILE - Secretary of State nominee Antony Blinken testifies during his confirmation hearing to be Secretary of State before the Senate Foreign Relations Committee on Capitol Hill in Washington, Jan. 19, 2021. (Graeme Jennings/Pool via AP)

Unified control of Congress also gives the legislative branch a greater ability to enforce government accountability. Most notably, the landscape for the unprecedented second impeachment trial of former President Donald Trump changes considerably with Democrats in control.

"There's no greater sign of accountability than Congress literally holding a presidential impeachment trial," Burgat said. "And we of course, have never seen one after the president has left office. So, it's the epitome of Congress sitting up for itself and making sure that the president is paying attention, or at least doesn't think of himself as above the law."

Despite their new majority in the Senate, Democrats will still need to attract 17 Republicans for the two-thirds majority needed to convict Trump and bar him from running again for federal office. But Democrats' overall lack of a significant majority could ultimately work to Biden's advantage, one analyst said.

David Barker, director of the Center for Congressional and Presidential Studies at American University, said, "The Biden administration is really fortunate to be in a perfect kind of position where they've got 50." 

Barker asserted that with such a narrow majority, Biden can more easily justify seeking centrist compromises with Republicans over the objections of liberal Democratic forces. "It's [more] easy for them to frankly, turn to the left of the party and say, 'Sorry' — and that's going to put them in a better political position."