A more thorough explanation:

The Mike O'Connor rule is a labor law doctrine that states that any unilateral changes made by an employer after a union victory in an initial-representation election, but before the employer's objections have been resolved, are automatic violations of the National Labor Relations Act if the employer's objections are rejected.

For example, if a union wins an election to represent workers at a company, but the employer objects to the election results, any changes made by the employer to the workers' wages, hours, or working conditions without bargaining with the union would be considered a violation of the law if the employer's objections are rejected.

The Mike O'Connor rule is important because it ensures that employers cannot make changes to workers' rights without first bargaining with their union representatives. This helps to protect workers from unfair treatment and ensures that their rights are respected.