Nancy Pelosi Re-Elected US House Speaker With Narrow Majority

House Democrats returned Representative Nancy Pelosi of California to the speakership on Sunday for what may be her final term, handing a tested leader control of the slimmest House majority either party has faced in two decades.

Ms. Pelosi secured 216 votes, narrowly topping the 209 of Representative Kevin McCarthy of California, Republicans’ leader. She managed to keep defections to just a handful, winning over several Democrats who had opposed her two years ago when Democrats had a more comfortable majority.

The nearly party-line vote punctuated an opening day marked more by precaution than pomp, as the 117th Congress convened for the first time under the threat of a deadly coronavirus pandemic that has rattled its ranks and the country. Several House members sick with Covid-19 missed the session altogether and others cast their vote from behind a plexiglass enclosure specially constructed in a gallery overlooking the chamber.

After two years as President Trump’s most outspoken Democratic antagonist, Ms. Pelosi will now be responsible for trying to shepherd through Congress as much of President-elect Joseph R. Biden Jr.’s agenda as possible, while maintaining her party’s majority ahead of next year’s midterm elections.

It will be no easy task. With her party in control of just 222 of 435 seats, Ms. Pelosi can afford to lose only a handful of Democrats on any given vote and faces a Republican opposition empowered by a better than expected showing in November’s election. She will also have to contend with a health crisis that can sideline lawmakers at any moment.

“I am confident that the Speaker’s election today will show a united Democratic Caucus ready to meet the challenges ahead, and that we are prepared to set our country on a new course,” Ms. Pelosi wrote Sunday morning in a letter to colleagues. She limited defections from her party to just a handful, winning over former moderate and progressive critics.

On the other side of the Capitol, the Senate convened an even more subdued opening day as both parties await a pair of runoff elections in Georgia on Tuesday that will determine which of them begins the year in control. The outcome could determine the fate of Mr. Biden’s legislative goals on climate change, taxes and health care; his response to the coronavirus pandemic; and his ability to fill his cabinet and influential federal judgeships.

Republicans currently have an edge, with 51 seats to Democrats’ 48. Democrats would have to sweep both races to draw the chamber to a tie and effectively take control when Vice President-elect Kamala Harris, who would cast tiebreaking votes when needed, is sworn in with Mr. Biden on Jan. 20.

With the coronavirus circulating rampantly, members-elect expected little of the pomp that usually accompanies Congress’s initial convening. Lawmakers took the oath of office and voted for speaker in small groups, rather than all together in the normally boisterous hall of the House. The architect of the Capitol had even constructed a small plexiglass enclosure in one of the galleries overlooking the chamber so that three lawmakers in a protective quarantine could vote in person but not mingle on the House floor.

Nor was there much promise that the partisan warfare that has seized the capital in recent years would soon subside with the new session. After they are sworn in, a growing cohort of Republican senators and House members plan to initiate a long-shot attempt on Wednesday to try to overturn Mr. Biden’s victory and deliver a second term to Mr. Trump. The attempt will fail, but only after it cleaves the Republican Party in two and further erodes confidence in Mr. Biden’s legitimacy among the president’s most ardent supporters.