Center-align the numbering, vertically, in the enumerate environment

Question

Imagine you have an enumerate environment and one of the items spans many lines. Normally, the numbering (e.g., 1., 2., 3., …) is aligned with the top of the item, i.e., the first line. How can I have it vertically aligned in the center?

Example:

\begin{enumerate}
\item this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that 
\item short line
\item short line
\item this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that 
\end{enumerate}

Answer 1

I suggest you encase the multi-line items in parboxes of width \linewidth.

\documentclass{article}
\usepackage{calc} % allow simplified syntax for length calculations
\begin{document}

\begin{enumerate}
\item \parbox{\linewidth}{%
this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that}
\item short ling
\item short ling
\item \parbox{\linewidth}{%
this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that this is a ling that}
\end{enumerate}

\end{document}