keeping the last line of one paragraph with the first line of the next paragraph or list in a \raggedbottom context

Question

I often introduce new text with the last line of a paragraph, terminated by a colon. Perhaps the text before and after is ordinary text (between pages 1 and 2 in the example), or the text thereafter is a list (between pages 3 and 4 in the example), or the first paragraph is within a list with the next one being in a nested list (between pages 5 and 6 in the example). I would like to keep the last line of the first paragraph with the subsequent paragraph because that last line is often of an introductory nature. How can I do this? (I know about \Needspace, but I don't know how to use it for a solution here.)

I believe this question makes most sense in a \raggedbottom-context; this is also where I need this resolved. Here is an example:

\documentclass{memoir}
\usepackage{lipsum}
\raggedbottom

\begin{document}

\lipsum[1-4]
Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text:

Some filler text. Some filler text.

\newpage

\lipsum[1-4]
Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text:

\begin{itemize}
\item Some text.
\item Some text.
\item Some text.
\end{itemize}

\newpage

\begin{itemize}
\item \lipsum[1-4]
\item Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Now a nested list:
    \begin{itemize}
    \item Some text.
    \item Some text.
    \item Some text.
    \end{itemize}
\end{itemize}

\end{document}

Here I would specifically like the last lines of pages 1, 3, and 5 kept together with the first lines of pages 2, 4, and 6, respectively. \nopagebreak works in the first case, but not in the two list cases.

Answer 1

Some filler text. Some filler text. Some filler text. Some filler text. Some filler text. Some filler text:
\widowpenalty=-5000 \nopagebreak
\begin{itemize}
\item Some text.
\item Some text.
\item Some text.
\end{itemize}

pushes

Some filler text:

To the top of page 4. The negative widow penalty encourages rather than discourages a break before the last line of the partial paragraph and the \nopagebreak stops it breaking before the list.