Here are the moderate Democrats who will have outsized influence over Biden’s agenda amid a slim majority in the Senate

• With a slim majority in the Senate, Biden’s agenda could often hinge on one or two Democrats. 
• Moderate Democrats like Joe Manchin and Kyrsten Sinema are poised to have overwhelming influence in the early part of Biden’s era.
• The debate over the filibuster has already shown why the narrow Democratic Senate majority will be a challenge.
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Joe Biden has been president for over a week, and congressional Democrats haven’t considered much of his agenda yet.

Democrats have control of the Senate for the first time in six years. Georgia runoff winners Raphael Warnock and Jon Ossoff, along with Alex Padilla, California’s former secretary of state, were sworn in by Vice President Kamala Harris on January 20. The ceremony finally materialized the party’s highly sought-after goal: control of the White House and Congress. 

Democrats have so far struggled to take advantage of that newfound power, dawdling somewhat in pushing legislation through. The delay has mainly stemmed from the Senate, which came to standstill because Minority Leader Mitch McConnell and Majority Leader Chuck Schumer feuded over the filibuster.

In a nutshell, McConnell wanted Schumer to promise to preserve the legislative tactic, which essentially functions as the minority’s check on the majority by allowing endless debate on a bill, often to delay or block its passage. Sixty senators are required in order to stop debate and vote on a bill. Many progressives in the Democratic Party have recently renewed calls for eliminating the filibuster.

Schumer was obstinate in the face of McConnell’s demands on the filibuster, but the Kentucky Republican ultimately backed off after two Democratic senators vowed to uphold the tool. Those two lawmakers, Joe Manchin and Kyrsten Sinema, along with several other moderate Democrats, are shaping up to have significant influence over Biden’s legislative priorities.

Besides the filibuster stalemate, the Senate has been busy confirming Biden's Cabinet picks and is also preparing for an impeachment trial for former President Donald Trump.

Biden, meanwhile, has signed dozens of executive orders, ranging from tackling the COVID-19 pandemic to climate change and racial injustice. Yet the power of the presidency can only go so far without congressional support.

One area that top Democrats have pledged to quickly deliver on is another coronavirus stimulus. Dubbed the "America Rescue Plan," Biden's $1.9 trillion package includes $1,400 one-time direct payments, aid for state and local governments, a goal to vaccinate 100 million Americans within his first 100 days in office, among other proposals. White House coronavirus advisor Andy Slavitt said this week that the Biden administration can achieve its vaccination goal without Congress, but added that the legislative body is needed to secure more funding to vaccinate all Americans.

However, Democrats are operating on slim majorities in both chambers and divided sentiment within the party, posing a challenge for Biden to implement his agenda. The president's major hurdle lies in the Senate because of the filibuster, which if employed would require support from at least 10 Republicans for his legislation to have any shot. Democrats have tools to work around it, such as a procedure known as budget reconciliation that only requires a simple majority of 51 to pass legislation. But that can only happen if Biden is able to unite all 50 senators in the Democratic caucus, which includes two independents - Bernie Sanders of Vermont and Angus King of Maine - to support his policy.

These are the moderate Senate Democrats who could influence much of Biden's legislation: 

• Joe Manchin
  • Manchin has been thrust into the spotlight in recent weeks after he pledged to McConnell that he would not eliminate the filibuster. The West Virginian is well known for his conservative voice in the party, hailing from one of the reddest states in the country and frequently voting with the GOP. He was the lone Democrat to vote to confirm Supreme Court Justice Brett Kavanaugh. Manchin's stances could threaten some of Biden's progressive ideas, especially when it comes to climate change. Manchin has also been skeptical of Biden's stimulus proposal. He's poised to be a major senator to watch in the Biden era.
• Kyrsten Sinema
  • Similarly, Sinema has come on the radar in light of her support to maintain the filibuster. She is one of two Democratic senators representing Arizona, a key swing state in the 2020 elections that flipped to Biden. Yet like Manchin, she has a record of voting with the GOP, making her vote crucial under the Biden administration.
• Chris Coons
  • Coons is one of Biden's closest allies in the Senate and represents the president's home state of Delaware. The senator had been considered to serve as Secretary of State, but Biden chose Anthony Blinken instead. "I need you in the Senate," Biden told Coons in a November 16 conversation. Coons, who's built a bipartisan reputation, is expected to wield substantial political power in Biden's term.
• Amy Klobuchar
  • Klobuchar is another moderate to keep an eye out for, as she's been closely linked to Biden's circle over the past several months. The former 2020 presidential candidate, who ran on her centrist, Midwestern background, quickly endorsed Biden after she dropped out of the race. Klobuchar was in the running to be Biden's vice presidential pick, but withdrew her name and said the president-elect should select a woman of color instead. The Minnesota senator had also been floated to serve in Biden's Cabinet. On Inauguration Day, Klobuchar played a key role in Biden's ceremony and delivered the opening address. 
• Jon Tester
  • Tester could become an important "yes" vote on Biden's legislation. Like Manchin, he also comes from a red state: Montana. Yet unlike Manchin, he hasn't voted with the GOP as much, despite Montana voting for former President Donald Trump in the 2016 and 2020 elections. Biden may be able to use this to his advantage and secure Tester's support on many of his policy positions.
• Michael Bennet
  • Though he dropped out of the race fairly early on, Bennet raised his national profile by running for president in 2020. The Colorado Democrat has garnered a reputation as a lawmaker who seeks to push ideas palatable to both parties, such as criminal justice reform, and could be a strong ally for Biden on the legislative front.
• Mark Warner
  • As chairman of the Senate Intelligence Committee, Warner is in one of the most important positions in Congress. The committee oversees the US intelligence community, which the Biden administration is working to repair after four years of relentless attacks from the Trump administration. The Virginia Democrat has a long record as a centrist, and will play a key role in discussions on threats to the US, including domestic terrorism.
• Jeanne Shaheen
  • Shaheen was at one point floated as a potential running-mate for Biden. The New Hampshire Democrat has a close relationship with the president: they've been friends for years and worked together on various legislation in the past. She could be a top ally for Biden in the upper chamber. 
• Bob Casey
  • Casey could be an ally for Biden on most issues, but has often stood out from others in his party due to his stance on abortion. In the past, the Pennsylvania lawmaker has described himself as a "pro-life Democrat" and in 2019 was one of just two Democratic senators  - the other being Manchin - to vote for a permanent ban on federal funding for most abortions. Biden during his campaign supported ending the Hyde Amendment, which bans federal funding from going to most abortions, but any such effort could face opposition from Casey.