Norman Ornstein is a resident scholar at the American Enterprise Institute.

The biggest surprise in November’s elections was the Democrats’ loss of seats in the House of Representatives. Indeed, there were two surprises: that the party suffered losses at all, and that there were so many — at least 12. Democrats will start the next Congress with a likely majority of only four seats, and that number will shrink to two for several months until special elections can be held when Reps. Cedric L. Richmond (D-La.) and Marcia L. Fudge (D-Ohio) leave for positions in the Biden administration.

Even that four-seat majority has its perils. One is short-term and is admittedly unlikely, but it involves the ability of the new House to vote remotely by proxy. When the new House convenes at noon on Jan. 3, all members will have to be physically present to be sworn in, and they will have to re-pass the rule that allowed the House to vote remotely. If, let’s say, five Democrats have covid-19 and are quarantined or hospitalized, or can’t make it to Washington, while all the Republicans can be present, the majority could rest temporarily with the GOP. What would then happen on Jan. 6, when Congress meets in joint session to affirm the electoral college results, is anyone’s guess.

But the implications of a razor-thin majority are likely to persist long after that. The House has not had a margin this close since after the 1930 election. That year, Republicans won 218 seats but had enough deaths before the convening of the new Congress in March — 14 in all — that Democrats were able to take the majority and hold it when they won a few of the special elections in the interim.

The Democrats’ impending mini-majority means there is no leeway for President-elect Joe Biden to choose any more House members for Cabinet positions or other key posts, and there will be heavy pressure put on California Gov. Gavin Newsom (D) not to choose one of the very attractive possible replacements in the House for Vice President-elect Kamala D. Harris’s Senate seat when it becomes vacant on Jan. 20. And, in the meantime, any glitch — an unexpected death or resignation, or even defection, could make a big difference.

Not only that: Simply having a majority does not mean power to do anything on the wish list of either the president or the speaker. For Nancy Pelosi, in a House where there is no likelihood on any significant issue of getting a single Republican vote, the California Democrat will have no leeway at all. The speaker will need the support of progressives such as Rep. Ilhan Omar (D-Minn.) and moderates such as Rep. Abigail Spanberger (D-Va.) — and all the Democrats across that wide spectrum. And lawmakers will always think about the next election in 2022, a midterm vote that usually goes against the party holding the White House, making those members from swing or close districts — most of them from the moderate wing of the party — especially antsy and fearful of controversial issues or votes.

Holding the majority in either house is huge. It means control over the agenda — what is brought to the floor and when and in what form, what amendments are allowed, and what does not come up; in the House in particular, it means using control of the Rules Committee to limit amendments and prevent the kind of “gotcha” votes that could make life more difficult for vulnerable Democrats in red or purple districts. It means control over committees, with their agendas and staff, and the ability to hold hearings, including investigations. It means the bully pulpit that comes with titles like speaker and senate majority leader.

It may sound paradoxical, but having the House majority will become even more consequential if Democrats win both of Georgia’s Senate seats in the Jan. 5 runoffs. Control of both houses and the White House at least opens the possibility of significant legislative action, in areas such as health care, tax policy, infrastructure and criminal justice reform. A 50-50 Senate, of course, would create the same challenge for the new majority leader, Charles E. Schumer (N.Y.), as the close margin does for Pelosi — the need to get approval from all Democratic senators, from Joe Manchin III (W.Va.) to Bernie Sanders (I-Vt.).

The Senate has had a 50-50 majority before, most recently in 2001, when party leaders Tom Daschle (D-S.D.) and Trent Lott (R-Miss.) adopted a power-sharing arrangement. If an even split is the result after the Georgia runoffs, we will see no power-sharing. The relationship between Schumer and Mitch McConnell (R-Ky.) is, at best, acrimonious, and tribal divisions and distrust in the Senate would not make that possible even if the two leaders had a better relationship.

But even if the Democrats’ Senate deficit is 51-49 or 52-48, covid-19 will make the numbers more shaky than we usually find. We could see majorities shift more than once in 2021. We are in a new territory where the nation’s priorities and those of the incoming president may rest on forces beyond the control of the politicians.

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