After she cast a vote against the motion to proceed to Mitch McConnell’s health care bill, Sen. Lisa Murkowski of Alaska received a threat from the Trump administration. The threat was delivered by the person most likely to strike fear into her, which in this case turned out to the Secretary of the Interior, Ryan Zinke. The Interior Department is very important to Alaska and important to Murkowski in particular because she chairs the Committee on Energy and Natural Resources and the Appropriations Subcommittee on Department of the Interior, Environment, and Related Agencies. She also serves on the Committee on Indian Affairs which oversees the Bureau of Indian Affairs which is an agency within the Department of the Interior.

Of course, this cuts both ways. If pretty much everything Murkowski does in the Senate has something to do with the Interior Department, it’s also true that she probably exercises more control over the Department than any other senator. A normal Interior Secretary would not mess with her.  The only limit on her ability to exact retribution is her self-interest in maintaining a good working relationship.

A more astonishing aspect of this, however, is that the White House instructed Secretary Zinke to issue the exact same threats to Sen. Dan Sullivan who also represents Alaska but voted with the administration on the motion to proceed.

Alaska Sen. Dan Sullivan said the call from Zinke heralded a “troubling message.”

“I’m not going to go into the details, but I fear that the strong economic growth, pro-energy, pro-mining, pro-jobs and personnel from Alaska who are part of those policies are going to stop,” Sullivan said.

“I tried to push back on behalf of all Alaskans. … We’re facing some difficult times and there’s a lot of enthusiasm for the policies that Secretary Zinke and the president have been talking about with regard to our economy. But the message was pretty clear,” Sullivan said. The Interior secretary also contacted Murkowski, he said.

Here are some of the ways that White House can make things uncomfortable for the two Alaskan senators:

Efforts and issues on the line include nominations of Alaskans to Interior posts, an effort to build a road out of King Cove through the Izembek National Wildlife Refuge, and future opportunities to drill in the Arctic National Wildlife Refuge and expand drilling in the National Petroleum Reserve-Alaska, among other regulatory issues that are a priority for Murkowski and Sullivan.

The other Republican who voted against the motion to proceed is Susan Collins of Maine. She has a different profile in the Senate, so a different messenger may have been used to issue threats of retribution. I don’t know whether she was contacted or not. But both she and Murkowski now have reasons to seriously consider bolting the Republican Party and caucusing with the Democrats. Murkowski is already half an independent, having been defeated in the Republican primary during her last reelection effort and winning nonetheless on a write-in slate. Susan Collins comes from a state famous for successful independent politicians, including her colleague Sen. Angus King who caucuses with the Democrats and served as an independent governor of the Lobster State.

If he’s doing his job, Chuck Schumer is now working on packages he can offer these senators that would make their transition as comfortable as possible. This has been done in the recent past, with Tom Daschle wooing Vermont Senator Jim Jeffords to his side back in 2001, and Harry Reid doing the same with Pennsylvania Senator Arlen Specter during President Obama’s first term.

As I was thinking about this, it occurred to me that neither Murkowski nor Collins would have enough incentive to jump alone, but they might jump together because it would create a 50-50 split in the Senate. And then I recalled that there was initially a 50-50 split in the Senate after the 2000 elections, which created a unique power-sharing arrangement. It didn’t last because the Bush administration so badly disrespected Sen. Jeffords that he quit the GOP and gave the Democrats an outright majority that lasted until after the 2002 midterms.

I wanted to understand how that power-sharing arrangement worked, so I consulted the congressional record and refreshed my memory. The story was a lot more interesting than I expected, so I’ll share some of it with you now.

The context was the contested 2000 presidential election which left the Democrats’ seething at the Supreme Court, the Senate evenly split, and partisan feelings at a modern-day high. The Republicans insisted that the true split was 51-50 in their favor since incoming Vice-President Dick Cheney was constitutionally empowered to break ties. The Democrats pointed out that the Constitution allowed the vice-president to break ties on votes on the floor, but not in committees. They insisted that the real split was 50-50 and that all committees, office space and funding had to be evenly split.

A compromise was struck between Trent Lott and Tom Daschle in which everything would indeed be evenly split but Lott would become the Majority Leader and Republicans would be the chairpersons on the committees and subcommittees. If a tie occurred in a subcommittee, it could still be advanced to the full committee, and if a tie occurred on a full committee, it could still be advanced to the floor.

Even some of the more moderate Republicans, like Sen. John Warner of Virginia, objected to this deal on the premise that if he were to take the responsibility of a chairman he ought to have the ability to advance bills without a partisan logjam. But Lott convinced them to relent, correctly assessing that nothing would get done in the Senate if the Democrats weren’t appeased.

There wasn’t much precedent for figuring out what should happen because, at least in modern times, the Senate had never been evenly split after an election before. But there was a situation that came close in 1953.

After Dwight Eisenhower was elected President in 1952, the Republicans took control of the Senate for the first time since 1932, but by the narrow margin of 49-47. Ohio Sen. Robert Taft became the majority leader. Before long, though, Sen. Wayne Morse of Oregon had a major disagreement with the Eisenhower administration, announced himself an independent, and tried to insist that he would not caucus with either side of the aisle but take his committee assignments from the Senate “as a whole.” When he discovered that this was magical thinking and he would get no committee assignments, he decided to caucus with the Democrats. This created a 48-48 split.

Shortly thereafter, Sen. Taft succumbed to cancer and the Democratic governor of Ohio appointed Thomas Burke to serve in his place. This then caused a 49-47 Democratic majority. As you might expect, the Democrats expected to take control of the Senate at that point, but it didn’t happen.

This is how Utah Sen. Bob Bennett explained it during the debate on the organizing resolution in January 2000.

Now this was the situation: Because the Republicans had organized the Senate with 49 Senators to begin with, they had organized it with a Republican majority on every committee. They held that Republican majority on every committee until Senator Taft died, and it switched.

At that point, Senator Morse–this I do remember–said, A, he had been elected as a Republican and, B, the Republicans controlled the administration and, therefore, in order to prevent the new President from being frustrated in his opportunities to get things through, he would, even though he had denounced his Republican party membership, vote with the Republicans on organizational issues, giving the Republicans 48, the Democrats 48, and with Richard Nixon in the chair giving the Republicans 49.

Here is the key point. Under those circumstances, the Democrats said: We will not ask for a realignment of the committees. We will allow the majority that was there on the committees to be maintained through the balance of this Congress.

So it was 48 Democrats, 47 Republicans, and 1 Independent, with the Independent vowing to vote against any organizational resolution the Democrats might bring forward, and of course Vice President Nixon would vote also that way, so the Republicans, even though they had only 47 seats, in a 96-seat Senate, maintained the chairmanships and a 1-vote margin on every committee.

Obviously, everything about what happened in 1953 was just slightly different from what happened in 2001. The most consequential difference was that the Senate started out split in 2001. The other very important difference was that Jim Jeffords wasn’t as charitable as Sen. Morse had been after his defection.

If Murkowski and Collins were to split the party now, the precedent would be more like 1953 than 2001 because the Senate has been organized with a Republican majority, not to accommodate an even split. However, if they were to vote with the Democrats on organizational matters, the precedent would also resemble 2001.

These precedents are key to gaming this scenario out correctly, because the Republicans would surely point back to 1953 as the only meaningful precedent, and with justification. They would argue that they they should retain majorities on all the committees and their better office space and higher levels of funding because that’s what had happened the last time even though in that case the Democrats eventually attained an outright majority.

The Democrats would argue that 2001 was the more appropriate precedent and point out that Morse’s decision to vote with the Republicans on organizational matters was discretionary and not the basis for a binding precedent.

Today’s Republicans would not likely yield on these issues and reach a compromise, at least not initially. And that makes it a little harder to recruit Murkowski and Collins in the first place, because they’d more clearly be moving from the majority to the minority.

So, there you have it. That’s all I can tell you about what would happen if Trump’s threats caused the Republicans to lose their majority in the Senate. Schumer should be working on it nonetheless, because it would improve his ability to stymie the Trump administration and make it more possible to win a majority after the 2018 midterms. But even if the effort were successful in the short-term, its impact probably wouldn’t be all that we might hope.