I'd like to be able to change (in particular, make smaller) the width of my table of contents in the article document class without altering the margins of the page. Is this possible??

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The "meta" answer to your question is that you can use the tocloft package to change the style of your ToC. (Or the memoir class, or KOMA-Script classes, etc.) But if you just want to change some margins, there's an easier approach:

\documentclass{article}
\usepackage{patchcmd}
\makeatletter
\patchcommand\@starttoc{\begin{quote}}{\end{quote}}
\makeatother
\usepackage{lipsum}
\begin{document}
\tableofcontents
\section{lipsum}\lipsum[1-10]
\section{lipsum}\lipsum[1-10]
\section{lipsum}\lipsum[1-10]
\section{lipsum}\lipsum[1-10]
\end{document}


The quote environment indents by, oh, 2.5em I think. If you need a different amount consider using changepage’s adjustwidth environment.

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