When it comes to making an endorsement of a presidential candidate, the most obvious thing to do is to pick the person you think is going to actually win. A new president will remember who supported them. They’ll also be more impressed by someone who stuck their neck out early when the outcome was still in doubt and their help could have plausibly made some difference.

It most cases this will give you the maximum influence to push your policies with the next White House. But there are obviously limitations on this. Endorsing a Republican because you believe they’ll be the next president is unlikely to get a progressive Democrat much, if any, benefit. The same is true on some issues if they endorse a moderate Democrat. In these cases, the net effect could be a loss of influence because going outside of your ideological lane will disappoint your followers and weaken your base of power.

To reduce the likelihood of this happening, it’s often a smart strategy to extract something of visible value in exchange for your endorsement. This could be a cabinet position for yourself or a close ally. It could be a public commitment from the candidate to work on one of your key issues.

So, when does it make sense to make an endorsement of someone who you think will not be the next president?

This is usually an easy decision when you think your party’s nominee is going to lose. You can still endorse them to signify where you stand and to do what is expected of you by both your supporters and your peers. There’s not much benefit if your assessment of the race is correct, but you avoid doing harm to yourself and could get a reward if things turn out better than you expect.

It’s a harder decision when the endorsement takes place during the nomination process itself, because you’re trading away influence with the eventual nominee and possible next president. What you get in return must be of equal or greater value, and that’s a hard test to meet.

For Elizbeth Warren, what does an endorsement of Bernie Sanders have to offer over the good will of Joe Biden?

That’s the decision she has to make now. Does she need the street-cred on the left a Sanders endorsement would maintain more than she needs some influence with a Biden administration? Is there something visible she can convince Biden to offer her that will smooth over some of the disappointment many progressives will feel? Is there something of real value on the merits that she couldn’t get in any other way?

For Biden, it should really not be that hard to find the tipping point here. It’s possible that the price is too high. Maybe he’s not ready to commit to putting Warren on the ticket and she won’t settle for anything less. But, short of that situation, he should be able to meet her requests without much difficulty. Her endorsement is probably worth a commitment to fill a cabinet position with a Warren ally, or to promise to set up some program or department like the Consumer Finance Protection Bureau.

Sanders has nothing to offer her except the good will of his supporters, which is worth something for anyone who wants to speak for the left. Perhaps this is important enough to Warren that it makes sense to simply make no endorsement at all. But that’s a pretty passive move. She has tremendous leverage right now, and it’s hard to believe that her best move is to not use it.