Democrats will soon have control of the U.S. Senate by the slimmest possible margin, to go along with a razor-thin margin of control in the House of Representatives and control of the White House.

Incumbent Kelly Loeffler (R-GA) has lost her bid to continue serving the final two years of Johnny Isakson’s expired term, falling about 81,000 votes (1.8 percent) behind challenger Raphael Warnock (D-GA). And Jon Ossoff (D-GA) has defeated incumbent David Perdue (R-GA) for a full six-year term by about 43,000 votes (1.0 percent). Both victories are above the recount threshold of 0.5 percent.

Once the Georgia Secretary of State sends the election certificates to the Senate, Warnock and Ossoff will be sworn in, and the Senate will have a party balance of 50-50. Under Senate precedents, in a tie situation, the party of the Vice President determines who gets to be called “Majority Leader” and with that title, who gets recognized first to lead debate, make motions, etc. Until noon on January 20, Vice President Pence means that Mitch McConnell (R-KY) is still Majority Leader. After noon on the 20th, Vice President Harris will mean that Chuck Schumer (D-NY) will be Majority Leader once the Senate seats Harris’s replacement, who will be Alex Padilla (D). (Harris may need to resign from the Senate before noon on the 20th to make things run more smoothly – soon-to-be-VP Al Gore resigned from the Senate on January 2, 1993, and Joe Biden resigned from the Senate on January 15, 2009.)

But just because Schumer, instead of McConnell, gets to be the one to speak first and make motions to proceed to bills and nominations starting at noon on the 20th, that doesn’t automatically mean that anything else changes. For example, the Senate is a “continuing body,” and the resolutions that elected members to committees in the last Congress (here and here) elected those members “for the One Hundred Sixteenth Congress, or until their successors are chosen.”

That means that as of today, everyone who was a member of a Senate committee last month is still a member of that committee today. The only changes so far have been the Senators whose terms ended on January 3. As a result, even after the Senate goes 50-50 and Kamala Harris becomes Vice President, Republicans will still hold a 16-14 majority on the Appropriations Committee, a 13-11 majority on the Commerce, Science and Transportation Committee, and a 11-10 majority on the Environment and Public Works Committee. (The Banking, Housing and Urban Affairs Committee, as well as the Finance Committee, are now tied.) (Pro tip: every business day, the Senate Calendar of Business prints updated committee membership lists.)

In order to designate new (Democratic) committee chairmen, and elect new members to committees, the Senate will need to pass a resolution, which is subject to debate (i.e. filibuster). The last time there was a 50-50 Senate, the parties ensured that every committee had equal numbers of Republicans and Democrats, but that the chairmanship of each would be held by the party of the Vice President. That precedent will probably continue.

Beyond that, at the start of the last 50-50 Senate, the two floor leaders negotiated a power-sharing arrangement (spelled out as S. Res. 8, 107th Congress). That agreement had five features:

1. The aforementioned 50-50 split of committee assignments, to be accompanied by a 50-50 split of committee salary money and office space.
2. A savings clause so that if the party balance shifted mid-Congress (which it did, in summer 2001), the agreement would be voided.
3. In the event of a tie vote in committee on any bill or nomination, S. Res. 8 provided expedited procedures for either party leader to move to discharge the bill or nomination from committee and put it on the calendar.
4. A requirement that no one could file cloture on a bill until it had been debated for at least 12 hours.
5. A promise by the two leaders to cooperate: “Both Leaders shall seek to attain an equal balance of the interests of the two parties when scheduling and debating legislative and executive business generally, and in keeping with the present Senate precedents, a motion to proceed to any Legislative or Executive Calendar item shall continue to be considered the prerogative of the Majority Leader, although the Senate Rules do not prohibit the right of the Democratic Leader, or any other Senator, to move to proceed to any item.”

That last provision was only possible because, at the time, the Republican Leader and the Democratic Leader got along fairly well. The current occupants of those positions don’t get along at all, and rarely speak.

In any new power-sharing agreement, the bit about discharging committees will be crucial. Parliamentary law says that in the event of a tie vote, the proposition (whatever it is) fails. Without an agreement for expedited motions to discharge committees that were tied and could not approve a bill or nomination, each motion to discharge a committee would be debatable and therefore subject to filibuster.

Although we don’t know precisely when the new committee chairmen and ranking minority members will be named, we do know who they will be:

But before anyone starts getting too celebratory about how the nominal change in Senate control will result in massive changes in federal transportation policy (see this way-too-early piece in Streetsblog for an example of the genre), remember that the Senate is still the Senate, and in a lot of ways, there isn’t much difference between a 51-49 Democratic Senate and a 51-49 Republican Senate (much less a 50-50 tie).

Most Senate committees still try to produce legislation on a bipartisan basis, and this is especially true of infrastructure legislation, which is normally produced by committees on a “Big Four” basis. The full committee chairman and ranking minority member, and the chairman and ranking minority member of the relevant subcommittee, draft a bill together from the ground up, and each one of those four has veto power over everything in the bill. When the four of them agree on a bill, they move it to the committee for amendment, but all four must agree on any amendment before it is accepted, or else all four of them have to oppose the amendment.

This is the process that the Senate Environment and Public Works Committee used in 2019 to produce its highway reauthorization bill, which was cheered by state DOTs and construction trade groups but was given a “F” rating by Transportation for America. That bill passed the committee by a unanimous vote, with everyone from Bernie Sanders (I-VT) to Mike Braun (R-IN) supporting the bill. Bills produced in this manner tend to be evolutionary, not revolutionary.

And before anyone gets too many hopes up about what Democratic control of the Senate will mean for Biden nominees, yes, it is much more likely that most Biden nominees can be rammed through the Senate than it was a week ago. But that does not mean that the process will be quick. We looked up the pace of major USDOT nominations when President Obama took office to serve as a benchmark for Team Biden:

To put these all on an equal footing, here are the number of elapsed days between the Obama press release announcing a nominee and that nominee’s confirmation by the Senate, and also the number of elapsed days between Obama taking office on January 20, 2009 and the nominee’s confirmation by the Senate.

And this was the pace when Obama had a Democratic Senate and a 60-vote supermajority. And this was also before the well had been poisoned on nominations in general by Harry Reid’s “nuclear option,” and before a handful of Democratic Senators started running for President in January 2017, which meant they were always competing to see who could cast the most anti-Trump roll call votes, which in turn meant the end of any nominees being allowed to be confirmed by voice vote. (Senate roll call votes are time-consuming and there are practical limits on how many roll calls can be held each week.) It seems unlikely that President Biden’s nominees, facing a 50-50 Senate and in a time where Republicans are certain to make Biden’s nominees wait the same number of days that Democrats made the Trump nominees wait, will go much quicker than that.