I have the code similar to the following:
<p>This is paragraph 1. Lorem ipsum ... </p>
<p>This is paragraph 2. Lorem ipsum ... </p>
<p>This is paragraph 3. Lorem ipsum ... </p>
<p>This is paragraph 4. Lorem ipsum ... </p>
<p>This is paragraph 5. Lorem ipsum ... </p>
<p>This is paragraph 6. Lorem ipsum ... </p>
I’d like to, without markup if possible, cause this text to flow into two columns (1-3 on the left, 4-6 on the right). The reason for my hesitation to add a column using a <div> is that this text is entered by the client via a WYSIWYG editor, so any elements I inject are likely to be killed later or inexplicably.
Using jQuery
Create a second column and move over the elements you need into it.
Update:
Or Since the requirement now is to have them equally sized. I would suggest using the prebuilt jQuery plugins: Columnizer jQuery Plugin
http://jsfiddle.net/dPUmZ/1/