complete, full, unreserved, or whole-hearted: a down-the-line endorsement.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Other Idioms and Phrases with down-the-line
Also, all along the line. All the way, throughout. For example, We've found numerous errors down the line. The first term dates from the mid-1900s, the variant from the second half of the 1800s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.