Chuck Schumer is fast rediscovering the joys of running a 50-50 Senate: stubborn centrists, irritated base, uncooperative opposition — and virtually no margin for error.

Why it matters: This will be his reality for two years unless he blows up the filibuster. Truth is, managing a divided government is a drag unless you dispense with rules and traditions.

• How Schumer handles the unusual power struggle will cement him as a powerful Senate leader or relegate him to political sideshow.

Between the lines: Several new power dynamics could further weaken his grip on the party.

• Moderates hold immense power, both because of the razor-thin majorities in Congress and President Biden's commitment to bipartisanship. They don't need to go through Schumer; instead, many have gone straight to Biden.
• Progressives are skeptical Schumer has their best interests at heart. That's in part why Sen. Bernie Sanders came out ahead of Schumer and publicly stated the party would be using the power move of budget reconciliation to pass coronavirus relief legislation.
• Minority Leader Mitch McConnell keeps trying to force him into a corner, most recently by holding up the Senate power-sharing accord, which effectively blocked Democrats from taking over the committees until Wednesday — two weeks after they regained the majority.
• Republicans are rallying around the idea that Democratic lawmakers and Biden's White House staff are pushing the president to be more partisan than he is. Like moderates, they, too, are skirting Schumer. They would rather deal with the president himself.

He's also facing trouble at home, as Politico points out.

• Rep. Alexandria Ocasio-Cortez and other progressives have flirted with the idea of challenging Schumer for his Senate seat. He's up for reelection in 2022.
• Andrew Cuomo, governor of Schumer's home state of New York, is pressuring the leader to ensure more money for state and local aid makes it into the final stimulus package.

The bottom line: All of these factions are closely watching Schumer to see how he reconciles their differing demands in the upcoming stimulus fight, which will be the first test of whether he can walk this tightrope without alienating members.