In a shocking upset that dramatically shifts the balance of power in Washington, Democrats Jon Ossoff and Raphael Warnock are projected to defeat two Republican incumbent senators in runoff elections in Georgia, ensuring Democratic control of the U.S. Senate for the first time in six years. CBS News projected Ossoff’s win as supporters of President Trump’s stormed the U.S. Capitol, forcing Congress to delay counting the Electoral College votes.

Ossoff and Warnock are the first Democrats Georgia has sent to the Senate since 2005, another signal that Georgia may be turning blue after President-elect Joe Biden won the state in November.

CBS News projects Warnock has defeated incumbent Senator Kelly Loeffler, who was appointed to fill a vacancy in 2019 by Georgia Governor Brian Kemp. Because this was a special election to replace former Senator Johnny Isakson, who stepped down for health reasons, Warnock will now complete Isakson’s term and run for reelection again in 2022.

CBS News projects Ossoff has defeated first-term Senator David Perdue, whose term expired on Sunday, by a narrow margin after vote-counting continued into Wednesday. They were two of the most expensive Senate campaigns in history, with Ossoff raising more than $139 million and Warnock over $125 million, according to Federal Election Commission records.

Ossoff and Warnock’s victories hand Democrats the narrowest possible majority in the Senate, and mean the party will have control of both Houses of Congress and the White House for the first time in 10 years. This dynamic will make it easier for Mr. Biden to begin implementing his agenda upon entering office. Senator Chuck Schumer, the current minority leader, is expected to replace Senator Mitch McConnell as majority leader.

“As Majority Leader, President-elect Biden and Vice President-elect Harris will have a partner who is ready, willing and able to help achieve a forward-looking agenda and deliver help and bold change to the American people,” Schumer said in a statement Wednesday morning.

Although the transition period has been rocky, with President Trump refusing to concede the election, a trifecta of power for Democrats once Mr. Biden is inaugurated should smooth his way. It all but guarantees that Mr. Biden’s Cabinet nominees will be confirmed quickly, without a Republican majority to delay the process.

But the Democratic majority will be razor thin. Democrats and Republicans will each have 50 votes, with Vice President-elect Kamala Harris casting any tie-breaking vote. Democrats will have to work with Republicans to pass any major legislation.

For now, Republicans will still have some power because of the legislative filibuster, which means that they can kill legislation if Democrats are unable to muster 60 votes to end debate on certain measures.

When the Senate majority leader or another senator seeks to end debate on a motion, he or she calls for “unanimous consent” to see if all 100 senators are willing to end debate and vote. If one senator objects, a cloture motion, which requires 60 votes, must be filed. If fewer than 60 senators support it, the bill fails.

Some Democrats have called for the elimination of the filibuster. Many Democrats support bills which almost certainly would not receive Republican support, such as a measure to make Washington, D.C., a state. However, many Democrats don’t want to get rid of the filibuster and fear it could set a dangerous precedent.

The Senate has previously done away with the filibuster for judicial nominations, which allowed for the Republican-led Senate to approve hundreds of Mr. Trump’s nominees to the federal bench without the 60-vote requirement. The Republican majority in the Senate had previously blocked dozens of President Obama’s nominations in the waning years of his term. With Democrats in control of the Senate, Mr. Biden will see his judicial nominees confirmed for the next two years at least.