The US Senate currently has a 50/50 split of Democratic (D) and Republican (R) caucus members. According to news reports, this has lead to "power sharing agreements" needing to be made between the Ds and Rs. Why is this necessary?
Since the vice president (VP) has tie breaking authority in the senate and supports Ds, why doesn't the VP simply break ties in favor of Ds so that the Ds have full power---making the power sharing agreement moot?
First, it's important to note that the VP is not a Senator and hence cannot vote unless the Senate is tied. A 50 seats + VP "majority" is not the same as an unequivocal 51 seats majority. This is an important distinction in practice if everything is passed strictly along party lines.
For instance, a 51 seats Democratic majority can accommodate for the absence of one Democratic Senator, as the Senate will still be in favour of Democrats 50D–49R. This will not be the case for a 50 seats + VP Democratic "majority" as there will be a Republican majority of 49D–50R if any one Democratic Senator is absent. Often, it may be difficult to ensure the presence of every single Senator for every single vote.
Even if every single Senator is present, a 50–50 Senate majority can still be difficult to govern if no power-sharing agreement is struck, especially since daily proceedings can be slowed down drastically. For instance, if the Senate perpetually votes along party lines, everything would require the Vice President to break a tie, thus necessitating the VP to always be present in the Senate, which is often not the case.
Then, there's the idea of fairness. A 50–50 Senate is, after all, evenly split, thus bringing us to the idea of negotiating a power-sharing agreement.
The last time the Senate was split 50-50, in 2001, lawmakers agreed on an organizing resolution that allowed both parties to share power. Under that deal, the parties agreed to split committee memberships and staff equally and changed the rules, making it so that if a tie vote prevented a measure from moving out of committee, either the majority or the minority leader could bring the bill to the Senate floor.
Reuters has an informative article regarding this:
DEMOCRATS CAN COUNT ON HARRIS’ VOTE. DO THEY REALLY HAVE TO STRIKE A POWER-SHARING AGREEMENT WITH REPUBLICANS?
No, but such a deal might help them get something like a normally functioning Senate, said Michael Thorning of the Bipartisan Policy Center.
“If Democrats really want to play hardball on Jan. 20, they don’t have to enter into a power-sharing agreement like this. They could leverage their 50 votes plus the vice president to try to run the Senate the way they see fit,” he said.
“They may find that under the current rules, that that is a very slow, very arduous way to run the Senate. You’d essentially be having a little skirmish over everything you wanted to do if Republicans really also wanted to play hardball,” Thorning said.
Former Senator Tom Daschle, who led the Democrats in 2001 in negotiating the power-sharing agreement with Lott, recommended that Schumer negotiate some kind of similar deal with McConnell.
“There’s only so much you can do with 51 votes, and you can’t expect the vice president to be sitting there, day after day, on every single issue, breaking the tie,” Daschle said.
“At the end of the day you’ve got to figure out a way to collaborate with the minority, because for all intents and purposes, there is no minority; you’re an equal. You’re equally represented in the Senate and that requires some equal voice, with regard to what the agenda is going to be.”
In short, the organizing resolution (power-sharing agreement) can be filibustered. Hence, in practice, 60 votes are needed to pass it, meaning it requires at least 10 Republican Senators to vote for it.
More information on this at Is there a contingency if a power sharing agreement cannot be made?
The Senate is an interesting political body, because the minority party has (had?) tools available to check the majority. In the past, there were two different types of filibuster: filibuster on appointments, and filibuster on legislation. These filibusters allowed the minority party to scuttle the majority party's agenda. And overcoming a filibuster required 60 votes, not 51.
Harry Reid blew up the filibuster on appointments during the Obama years, when Democrats grew frustrated with Republican attempts to block all Obama's appointments. He left filibuster on Supreme Court appointments in place, but eliminated the maneuver for all other positions. This gambit was dubbed "The Nuclear Option," as it basically triggered a power struggle battle royale that's continued to this day.
Once Republicans seized control during Trump's years, Mitch McConnell responded to Reid's move with one of his own: he blew up the filibuster on Supreme Court appointments. This is why Democrats were powerless to stop Gorsuch, Kavanaugh, and Barrett. (It's also why Republicans will be powerless to stop Stephen Breyer's replacement from going through, so stand by for those fireworks!)
[see: https://www.npr.org/2017/04/06/522847700/senate-pulls-nuclear-trigger-to-ease-gorsuch-confirmation]
That leaves the filibuster on legislation as the only tool available to the minority. Because the legislative filibuster stands, Democrats will not be able to pass any legislation through the Senate without Republican help. They only have 50 votes, and 60 are needed to vote down the filibuster. Harry Reid had more than 50 votes, so he was able to simply change the rules and eliminate the filibuster on appointments. Mitch McConnell had more than 50 votes, so he was able to change the rules and eliminate filibuster on Supreme Court appointments. But Chuck Schumer only has 50 votes. Remember, the VP only gets to vote in the case of a tie. And even though there is a 50/50 split in the Senate right now, there are a few Democratic senators who simply will not vote the party line for the sake of "party agenda." Hence, Chuck Schumer cannot simply change the rules and eliminate the legislative filibuster.
Senator Joe Manchin of West Virginia has become somewhat famous for frustrating his fellow Democrats with his truly centrist voting record. He is on record rejecting the idea of changing the Senate rules to eliminate the legislative filibuster, stating "We've harmed the Senate enough."
[see: https://www.nytimes.com/2020/11/30/us/politics/joe-manchin-interview.html]
Considering Manchin's stance, Democrats are actually 49/51 at a maximum when it comes to overcoming minority opposition and ramming through sweeping left-wing legislation. That already takes Harris' vote as VP off the table, since there is no tie.
Also, there's a new Manchin in town! Kyrsten Sinema of Arizona has also indicated she'd vote against changing the rules on overcoming legislative filibuster. She's allied with Manchin on this stance.
[see: https://www.politico.com/news/2021/01/21/democrats-mcconnell-filibuster-460967]
Considering where Sinema stands, Democrats are actually 48/52 at a maximum when it comes to overcoming minority opposition and ramming through sweeping left-wing legislation.
Democrats cannot overcome the legislative filibuster with the party's current Senate personnel, and Kamala Harris' vote is moot on the issue because there is no tie. The only way they could pass legislation would be to actually negotiate well enough, in good faith, to peel away 10 Republicans to vote with them.
So hopefully that helps you understand why 50/50 control in the US Senate necessitates a power sharing agreement right now. Senators are individuals, and some of them are (thankfully) more loyal to their constituents than to their parties, meaning 50/50 membership doesn't necessarily mean 50/50 votes. Neither party truly has the upper hand right now. Civility and negotiation must be the name of the game to get anything done, and the Schumer/McConnell talks are the very beginning of restoring the requisite level of decorum to our government...hopefully.
Update: In light of recent political happenings, a person might have questions as to how a $1.9T package was just passed through the Senate on a party-line vote, considering what I've written above. Why were 51 votes all that were necessary? What happened to these claims that Democrats would have to negotiate with Republicans? The answer is actually very simple: Democrats used the process by which Congress sorts out the budget in order to pass this through. That process is called "budget reconciliation," and the legislative filibuster does not apply to it because there is a baked-in limit on debate during budget reconciliation.
None. The Democrats are now the official Majority Party in the Senate, exactly the same as the Republicans were the majority party last month. That means that no matter who shows up to vote on any given day, Chuck Schumer decides who gets to talk and what they vote on. Likewise, only Democrats get to make committee assignments. Go to the US Senate page under Leadership: Democrat Leahy is the President-pro-tem and the Democrats have 6 extra leadership positions. There's no special "you're only in charge because of the VP" power-sharing rules.
Talk about a power-sharing agreement is two things. One, they always share power. The other party always gets a chunk of good committee assignments. The Armed Services Committee is generally 50/50. "In a bipartisan agreement" are the most heart-warming words in politics.
The other is the practicality of a thin majority. Everything still needs to be voted on, daily. Senators have emergencies, change sides, die... , and they're independent people whose constituents write letters. The numbers are more like 50+1 +/-5 vs. 50 +/-5. Any amount of senators in the low 50's is worrisome and you want to make nice with the minority.
For all intents and purposes, the President of the Senate (normally the VP) has a half vote. Not enough to affect the outcome either way, unless the voting Senators are equally split -- then that "half vote" is everything.
And remember, even though party-line voting has become more and more common lately, not everyone will vote the party line on every issue. Some will "cross the aisle".
The difference difference between a 51 seat majority and a 50 seat + VP “majority” is one senator, with everything that hinges on that.
