To show a likelihood of success on the merits, you need to convince a federal judge, working only from the papers you file, that you will probably win your underlying case once all the evidence is in. That means pairing a specific sworn factual record with a legal memorandum that walks through every element of your claim and shows, element by element, why the law and the available facts favor you. A plausible argument is not enough. Most federal courts require a “substantial likelihood” of success, which means more likely than not on both the law and the facts as they currently stand.
What a Judge Is Actually Deciding
The judge is not resolving the case. At the preliminary injunction stage there has been no discovery, no depositions, and no cross-examination. The court is making a prediction about where the case is headed based on a limited early record. Rough as that sounds, “rough” does not mean lenient. The Supreme Court in Winter v. Natural Resources Defense Council, Inc. described preliminary injunctions as “extraordinary” remedies and said a plaintiff must make “a clear showing” of entitlement to relief.1Justia. Winter v. Natural Resources Defense Council, Inc., 555 U.S. 7 (2008)
In practice, judges look for a clear indication that you hold the stronger position, not merely an arguable one. If the law genuinely cuts both ways or the facts you can prove at this stage are evenly split with what the other side can show, the substantial-likelihood standard usually is not met.
Build the Factual Record With Sworn Statements
Everything the judge knows about your case comes from what you file with the motion, so the documents do all the work. Federal Rule of Civil Procedure 65 specifically references affidavits and verified complaints as the foundation for factual claims in injunction motions.2Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders An affidavit is a written statement made under oath. A verified complaint is a lawsuit filing in which the plaintiff swears the factual allegations are true. Either establishes facts the court can rely on.
Specificity is what separates a useful affidavit from a wasted one. Judges discount vague or conclusory statements. An affidavit saying “I will be harmed if this continues” tells the court nothing. One that identifies the exact conduct, dates, dollar figures, witnesses, and consequences gives the judge something to work with. Think about every factual assertion in your legal argument and ask whether a sworn statement in the record actually supports it. If not, the argument is floating.
Documentary evidence does the same job from a different angle. Contracts, emails, financial records, photographs, inspection reports, and similar materials let the judge verify what the affidavits describe. Attach them as exhibits and reference them precisely in the sworn statements and brief.
Map the Evidence to Each Element of Your Claim
The legal memorandum is where the merits showing lives or dies. A judge reading it should be able to answer, for every element of your underlying cause of action, two questions: what is the governing law, and what evidence in the record satisfies that element right now.
A workable structure walks through the claim element by element. For each one, state the rule with authority, identify the facts in the affidavits and exhibits that meet it, and address the obvious counterargument. Judges notice when a brief ignores the weak spots in a case. Addressing them directly, with existing case law, is more persuasive than hoping the court will not see them. The brief should also include a clean statement of facts drawn from the sworn record so the court can see the story without hunting through exhibits.
Submit a proposed order along with the motion that describes the specific relief you want in concrete terms. Vague requests undercut credibility on the merits because they suggest you have not thought through what you are actually asking a court to do.
Know the Standard That Applies to Your Request
The baseline is substantial likelihood of success, but what counts as sufficient shifts depending on what you are asking the court to do and which circuit you are in.
Mandatory Versus Prohibitory Relief
Courts distinguish between injunctions that maintain the status quo (prohibitory) and those that force someone to take affirmative action (mandatory). Several federal circuits, including the Second, Fifth, Seventh, Ninth, and Tenth, apply a heightened standard when you seek a mandatory injunction, requiring a stronger showing on the merits than a typical prohibitory order demands. Not every circuit draws this line, but if your motion asks the court to compel action rather than prevent it, build the record expecting more skepticism.
The Serious-Questions Approach After Winter
Before Winter, several circuits used a sliding scale: if the balance of hardships tipped sharply in your favor, you could get by with something less than a full likelihood of success as long as you raised “serious questions” going to the merits. Winter cast doubt on that framework by insisting that irreparable harm must be likely, not merely possible, and by describing all four factors in mandatory terms.1Justia. Winter v. Natural Resources Defense Council, Inc., 555 U.S. 7 (2008) Some circuits have read Winter as eliminating the sliding scale entirely. Others have preserved a modified version, holding that the serious-questions test survives as long as the movant still shows irreparable harm is likely rather than merely possible. Research the current rule in your circuit before you decide how heavily to lean on the balance of hardships. Getting it wrong can cost you the motion.
Stays Pending Appeal
If you are seeking a stay rather than a preliminary injunction, the merits question becomes whether you have made a strong showing of likely success on appeal, not at trial. The Supreme Court set out that standard in Nken v. Holder, alongside the same irreparable-harm, balance-of-hardships, and public-interest factors.3Legal Information Institute. Nken v. Holder, 556 U.S. 418 (2009) The showing is similar in form but focused on identifying legal error in the ruling you are challenging, not on the strength of the underlying claim in the abstract.
The Merits Showing Is Necessary But Not Sufficient
A strong merits showing alone will not get you an injunction. The Winter test has four parts, and failing on any one of them can sink the motion:
- Likelihood of success on the merits.
- Likely irreparable harm without the injunction, meaning harm money cannot fix. Reputation loss, free speech violations, and irreversible environmental damage typically qualify. Pure financial losses usually do not, unless they would be so devastating that no later damages award could make you whole.
- Balance of equities tipping in your favor.
- Public interest served by the relief.
There is also a cost that catches many people off guard. Rule 65(c) requires you to post a security bond before the court will issue a preliminary injunction or TRO. The amount is up to the judge, and if you cannot post it, the injunction effectively dies no matter how strong your merits showing. Raise any financial hardship with the court early, because some judges will consider ability to pay when setting the amount. The federal government and its agencies are exempt from the bond requirement.2Legal Information Institute. Federal Rules of Civil Procedure Rule 65 – Injunctions and Restraining Orders
Common Reasons Merits Showings Fail
Patterns repeat. Affidavits make legal conclusions instead of stating facts. The brief argues the equities instead of marching through the elements of the claim. Exhibits are attached without being tied to any specific factual assertion. The movant ignores a controlling case the other side will certainly cite. The proposed order asks for sweeping relief that goes beyond what the pleaded facts justify.
Each of these invites the judge to conclude that the case is not as strong as the motion claims. The fix in every instance is the same: tighten the connection between what you can prove right now, under oath or with documents, and what the law requires you to prove to win the underlying claim. That connection is the merits showing.