“Dyed in the wool” is a phrase referring to people who hold very strong opinions and are unwilling to change them. Synonyms include “uncompromising” and “inveterate.” In politics, people might be can be referred to as “dyed in the wool Democrats” or “dyed in the wool Republicans.”
Merriam Webster notes that the phrase was first used in its modern sense in 1580. Merriam Webster says that in the 16th century, writers began to use the expression to discuss ways that “children could, if taught early, be influenced in ways that would adhere throughout their lives.” The phrase was used in its political sense as early as the beginning of the 19th century, when Daniel Webster complained about a certain type of Democrat whose views were “as unyielding as the dye in unspun wool.”
In its literal sense, “dyed in the wool” means that the wool has been dyed before it is spun into thread. This produces a strong and long-lasting color. Metaphorically, dyed in the wool means that someone’s opinions were formed and set at an early stage in their development and that they can’t be washed away.
In 1870 Frederick Douglass delivered a speech to new voters, urging them to vote their conscience; he described himself as a “Republican dyed in the wool” but told his audience that they had an absolute right to vote as they saw fit:
I hear some men say that if the black man, in this enlightened age, should vote the Democratic ticket let him be denounced. Gentlemen I do not share that opinion at all. 1 am a Republican – a Black Republican dyed in the wool- and I never intend to belong to any other than the party of freedom and progress. But if one of my colored fellow-citizens chooses to think that his interests and rights and the interests of the country can be better sub-served by giving his vote against the Republican party, I, as an American citizen, and as one desirous to learn the first principles of free government, affirm his right-his undoubted right-to vote as he chooses.
Dyed in the wool can be used in either a positive or a negative sense, depending on who is speaking. For example, when President Obama nominated Sonia Sotomayor to the Supreme Court, some leftists complained that Sotomayor was not a reliable, or dyed in the wool, liberal herself. Sotomayor did not have a strong liberal record on issues like abortion, same-sex marriage, and the death penalty. “The fact that she hasn’t gone off on these sorts of questions I think shows that honestly she’s not a dyed in the wool liberal,” Thomas Goldstein, a leading appellate attorney, told Politico, adding, “There are places where Sotomayor will be more conservative than Souter.”
In contrast, in 2018 the chair of the Pennsylvania GOP asserted that Conor Lamb, who was then running for Congress, was a “dyed in the wool liberal” and a staunch supporter of Nancy Pelosi. The implication was that Lamb was trying to portray himself as more centrist than he actually was, and that his true colors would show through after election.