The National Labor Relations Board announced on Friday that it was dropping its politically charged case against Boeing, in which it had accused the company of violating federal labor law by opening a new aircraft production plant in South Carolina instead of Washington State.

The labor board’s acting general counsel, Lafe Solomon, said he had decided to end the case after the union that represents 31,000 Boeing workers in Washington urged the board to withdraw it. That union, the International Association of Machinists and Aerospace Workers, had originally asked the board to file the case, but changed its mind after striking a deal with Boeing last week to raise wages and expand jet production in Washington.

The political conflagration ignited by the case will not be extinguished so easily.

After Mr. Solomon brought the case in April, Republican lawmakers and presidential candidates called it a prime example of regulatory overreach by the Obama administration, arguing that federal officials should not be telling companies where they can or cannot build factories. Congress held hearings and demanded thousands of pages of documents. The case also enraged South Carolina officials, who saw it as an insult to one of their greatest economic development achievements.

On Friday, many of those critics said that although they were happy to see the case dropped, they would press forward with attempts to hobble the board, which oversees efforts by private sector employees to unionize and bargain collectively and seeks to ensure that neither unions nor employers violate the laws governing such activities. The board’s five members and top staff officials are appointed by the president.