% pandoc -f latex -t native --quiet
\begin{tabularx}{\linewidth}{|c|c|c|}
\hline
  Column Heading 1
  & Column Heading 2
  & Column Heading 3 \\
\hline
  Cell 1.1 
  & Cell 1.2
  & Cell 1.3 \\
\hline
  Cell 2.1 
  & Cell 2.2
  & Cell 2.3 \\
\hline
  Cell 3.1 
  & Cell 3.2
  & Cell 3.3 \\
\hline
\end{tabularx}
^D
[Table [] [AlignCenter,AlignCenter,AlignCenter] [0.0,0.0,0.0]
 [[Plain [Str "Column",Space,Str "Heading",Space,Str "1"]]
 ,[Plain [Str "Column",Space,Str "Heading",Space,Str "2"]]
 ,[Plain [Str "Column",Space,Str "Heading",Space,Str "3"]]]
 [[[Plain [Str "Cell",Space,Str "1.1"]]
  ,[Plain [Str "Cell",Space,Str "1.2"]]
  ,[Plain [Str "Cell",Space,Str "1.3"]]]
 ,[[Plain [Str "Cell",Space,Str "2.1"]]
  ,[Plain [Str "Cell",Space,Str "2.2"]]
  ,[Plain [Str "Cell",Space,Str "2.3"]]]
 ,[[Plain [Str "Cell",Space,Str "3.1"]]
  ,[Plain [Str "Cell",Space,Str "3.2"]]
  ,[Plain [Str "Cell",Space,Str "3.3"]]]]]

% pandoc -f latex -t native --quiet
\begin{tabularx}{\linewidth}{|X|c|p{0.25\linewidth}|}
\hline
  Column Heading 1
  & Column Heading 2
  & Column Heading 3 \\
\hline
  Cell 1.1 
  & Cell 1.2
  & Cell 1.3 \\
\hline
  Cell 2.1 
  & Cell 2.2
  & Cell 2.3 \\
\hline
  Cell 3.1 
  & Cell 3.2
  & Cell 3.3 \\
\hline
\end{tabularx}
^D
[Table [] [AlignLeft,AlignCenter,AlignLeft] [0.0,0.0,0.25]
 [[Plain [Str "Column",Space,Str "Heading",Space,Str "1"]]
 ,[Plain [Str "Column",Space,Str "Heading",Space,Str "2"]]
 ,[Plain [Str "Column",Space,Str "Heading",Space,Str "3"]]]
 [[[Plain [Str "Cell",Space,Str "1.1"]]
  ,[Plain [Str "Cell",Space,Str "1.2"]]
  ,[Plain [Str "Cell",Space,Str "1.3"]]]
 ,[[Plain [Str "Cell",Space,Str "2.1"]]
  ,[Plain [Str "Cell",Space,Str "2.2"]]
  ,[Plain [Str "Cell",Space,Str "2.3"]]]
 ,[[Plain [Str "Cell",Space,Str "3.1"]]
  ,[Plain [Str "Cell",Space,Str "3.2"]]
  ,[Plain [Str "Cell",Space,Str "3.3"]]]]]

% pandoc -f latex -t native --quiet
\begin{tabularx}{\linewidth}{|b{0.25\linewidth}|c|m{0.25\linewidth}|}
\hline
  Column Heading 1
  & Column Heading 2
  & Column Heading 3 \\
\hline
  Cell 1.1 
  & Cell 1.2
  & Cell 1.3 \\
\hline
  Cell 2.1 
  & Cell 2.2
  & Cell 2.3 \\
\hline
  Cell 3.1 
  & Cell 3.2
  & Cell 3.3 \\
\hline
\end{tabularx}
^D
[Table [] [AlignLeft,AlignCenter,AlignLeft] [0.25,0.0,0.25]
 [[Plain [Str "Column",Space,Str "Heading",Space,Str "1"]]
 ,[Plain [Str "Column",Space,Str "Heading",Space,Str "2"]]
 ,[Plain [Str "Column",Space,Str "Heading",Space,Str "3"]]]
 [[[Plain [Str "Cell",Space,Str "1.1"]]
  ,[Plain [Str "Cell",Space,Str "1.2"]]
  ,[Plain [Str "Cell",Space,Str "1.3"]]]
 ,[[Plain [Str "Cell",Space,Str "2.1"]]
  ,[Plain [Str "Cell",Space,Str "2.2"]]
  ,[Plain [Str "Cell",Space,Str "2.3"]]]
 ,[[Plain [Str "Cell",Space,Str "3.1"]]
  ,[Plain [Str "Cell",Space,Str "3.2"]]
  ,[Plain [Str "Cell",Space,Str "3.3"]]]]]