In the process of decline or ruin, as in If she quit now, her career would be on the skids. The skids here are runners such as those on a sled, enabling one to go downhill quickly. [c. 1920]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.