Ya - you are going to have a hard time with any kind if wrongful termination suit because DC courts have upheld employment-at-will (here is the Wikipedia definition):
"At-will employment is a doctrine of American law that defines an employment relationship in which either party can break the relationship with no liability provided there was no express contract for a definite term governing the employment relationship and that the employer does not belong to a collective bargain (i.e. a union). Under this legal doctrine:
any hiring is presumed to be "at will"; that is, the employer is free to discharge individuals "for good cause, or bad cause, or no cause at all," and the employee is equally free to quit, strike, or otherwise cease work.[1]
Several exceptions to the doctrine exist, especially if unlawful discrimination is involved regarding the termination of an employee (this is a type of "public policy exception", since it is a violation of federal laws in EEO).
DC does have an "implied contract" exception, but if you read the definition and apply it to your case, it would be a tough case for you to make:
"Under the implied contract exception, an employer may not fire an employee "when an implied contract is formed between an employer and employee, even though no express, written instrument regarding the employment relationship exists."[9] Proving the terms of an implied contract is often difficult, and the burden of proof is on the fired employee. Implied employment contracts are most often found when an employer's personnel policies or handbooks indicate that an employee will not be fired except for good cause or specify a process for firing. If the employer fires the employee in violation of an implied employment contract, the employer may be found liable for breach of contract."
I would think that your best shot here would be if your employer has a strong record of following a personnel policy or handbook with a detailed process for termination. Of course, if it is a small company with a small number of employees, there is much less to go on. And, you also have the challenge that the employee who is replacing you has a lot of experience (and thus, it will be hard for you to demonstrate that there is no cause whatsoever for your employer to choose him over you in terms of pure qualifications and experience).
If you were working in one of the "good faith and fair dealing" exception states (Alabama, Alaska, Arizona, California, Delaware, Idaho, Massachussetts, Montana, Nevada, Utah and Wyoming), you would probably have a case. "Just cause" is the basic standard that labor unions typically push for in their labor contracts (and has been adopted by a few states).
"In the workplace, Just Cause is a burden of proof or standard that an employer must meet to justify discipline or discharge. Just Cause usually refers to a violation of a company policy or rule. In some cases, an employee may commit an act that is not specifically addressed within the employers policies but one of which the employer believes warrants discipline or discharge. In such instances, the employer must be confident that he can defend his decision."
So - if DC was a "just cause" state, your employer would have to prove that you committed policy or rule violations in order to terminate you. But, DC is unfortunately not one of the states that grants just cause exceptions.
