Modify the header on tufte-handout

Question

I am using the tufte-handout documentclass and the title of my document is 101 characters. Consequently the header on the pages following page one flow over to a second line in the header.

If my title is, "This is the title of the paper: An inquiry into something interesting to talk about in order to finish" would it be possible to just have the first part of the title appear in the header (i.e. 'This is the title of the paper')?

Here is my preamble:

\documentclass{tufte-handout}

%\geometry{showframe}% for debugging purposes -- displays the margins

\usepackage{amsmath}

% Set up the images/graphics package
\usepackage{graphicx}
\setkeys{Gin}{width=\linewidth,totalheight=\textheight,keepaspectratio}
\graphicspath{{graphics/}}

\title{This is the title of the paper: An inquiry into something interesting to talk about in order to finish}
\author{John Doe}
\date{}  % if the \date{} command is left out, the current date will be used

% The following package makes prettier tables.  We're all about the bling!
\usepackage{booktabs}

% The units package provides nice, non-stacked fractions and better spacing
% for units.
\usepackage{units}

% The fancyvrb package lets us customize the formatting of verbatim
% environments.  We use a slightly smaller font.
\usepackage{fancyvrb}
\fvset{fontsize=\normalsize}

% Small sections of multiple columns
\usepackage{multicol}

% Provides paragraphs of dummy text
\usepackage{lipsum}

% These commands are used to pretty-print LaTeX commands
\newcommand{\doccmd}[1]{\texttt{\textbackslash#1}}% command name -- adds     backslash automatically
\newcommand{\docopt}[1]{\ensuremath{\langle}\textrm{\textit{#1}}\ensuremath{\rangle}}% optional command argument
\newcommand{\docarg}[1]{\textrm{\textit{#1}}}% (required) command argument
\newenvironment{docspec}{\begin{quote}\noindent}{\end{quote}}% command specification environment
\newcommand{\docenv}[1]{\textsf{#1}}% environment name
\newcommand{\docpkg}[1]{\texttt{#1}}% package name
\newcommand{\doccls}[1]{\texttt{#1}}% document class name
\newcommand{\docclsopt}[1]{\texttt{#1}}% document class option name
\titlespacing*{\chapter}{0pt}{5pt}{40pt} 
\begin{document}

Answer 1

Precisely for these cases, in tufte-handout the command \title has an optional argument which is used to typeset its content to the header:

\documentclass{tufte-handout}
\title[An inquiry into something interesting]{This is the title of the paper: An inquiry into something interesting to talk about in order to finish}
\usepackage{blindtext}

\begin{document}
\maketitle
\blindtext\blindtext\blindtext\blindtext
\end{document}

Answer 2

The tufte class save the title, which is to be displayed in the header in a macro called \plaintitle. Hence renewing the definition of this macro you can place your custom stuff in the header.

\documentclass{tufte-handout}
\title{This is the title of the paper: An inquiry into something interesting to talk about in order to finish}
\renewcommand\plaintitle{This is the title of the paper}
\usepackage{blindtext}
\begin{document}
\blindtext
\end{document}