Two Democratic senators were sworn in on Wednesday and reduced the Republican majority in the upper chamber to a narrow 51-49, just as Republicans are getting ready to battle with Democrats on government spending, immigration reform and other key issues.

Doug Jones was sworn in after winning his race in December against Roy Moore to become the first Democrat elected to represent Alabama in decades.

Another Democrat, former Minnesota Lt. Gov. Tina Smith, also took her seat in the Senate on Wednesday, replacing fellow Democrat Al Franken, who resigned amid sexual assault allegations. Gov. Mark Dayton selected Smith to replace Al Franken, who was pressured to resign after several women accused him of groping them over the past decade.

Vice President Mike Pence administered the oath of office at noon to both Jones and Smith.

Sens. Bernie Sanders, I-Vt., and Angus King, I-Maine, are Independents, but are functionally Democrats and give that party 49 votes.

It was Jones' victory that gave Democrats the extra seat in the Senate, as he will take the seat formerly held by Attorney General Jeff Sessions. Jones will succeed Luther Strange, a Republican who was appointed to take over for Sessions. Strange failed to win the special election primary earlier this year by losing to Moore, who then lost to Jones after several allegations of sexual misconduct, including the pursuit of teenage girls when he was in his 30s.

The two new lawmakers took the oath on the Senate floor and then left for a ceremonial swearing in the Old Senate Chamber, located down the hall.

The ceremony brought a rare gathering of vice presidents. In addition to Pence, former Vice President Joe Biden appeared in the Capitol to accompany Jones, a longtime friend.

Walter Mondale, a Minnesotan who served as vice president under Jimmy Carter, accompanied Smith.

VP Mike Pence talks with former VPs Joe Biden and Walter Mondale. (Pic courtesy: Alyssa Farah, press secretary to Pence)

Smith becomes the 22nd woman in the Senate, an all-time high.

But Smith's seating is still controversial among Democrats, some of who are still grousing that Franken was forced out prematurely. Unlike in past instances of sexual misconduct allegations, the Senate ethics panel never completed an investigation of the accusations involving Franken, although an inquiry was opened.

David Axelrod, a former senior advisor to President Obama, said he believes Franken was “sacrificed” by Democrats to increase their chances of beating Moore in Alabama.

“Perhaps an ethics review would have led to the same result, but Franken never got a hearing,” Axelrod tweeted about an hour before Smith took the Senate oath.

The swearing-in took place as the Senate convened for the second session of the 115th Congress, a year when midterm election politics is expected to influence legislative outlook.

In addition to immigration and spending measures, lawmakers hope to consider an infrastructure bill as well as measures to replace the failing healthcare law. The bare majority will make it bipartisanship more likely and necessary in the upper chamber, where 60 votes are required to pass most legislation.

"I don't think most of our Democratic colleagues want to do nothing, and there are areas, I think, where we can get bipartisan agreement,” Majority Leader Mitch McConnell, R-Ky., said recently when asked about the new party ratio in the Senate.