You can use the HTML non-breaking space, &nbsp (or if you prefer hexadecimal, &#x00A0). The Wikipedia article says:

In certain formats (such as HTML), it also prevents the “collapsing” of multiple consecutive whitespace characters into a single space.

So for example, the markdown:

 1&nbsp;2&nbsp;3&nbsp;4<br>
 1&nbsp;&nbsp;2&nbsp;&nbsp;3&nbsp;&nbsp;&nbsp;4

renders as:

1 2 3 4
1  2  3   4

But since everything outside a <code> or <pre> block is rendered with a proportional-width font, you may find alignment across multiple lines to be tricky; in that case, using <code> blocks is probably your best bet.

You can use the HTML non-breaking space,   (or if you prefer hexadecimal,  ). The Wikipedia article says:

In certain formats (such as HTML), it also prevents the “collapsing” of multiple consecutive whitespace characters into a single space.

So for example, the markdown:

 1&nbsp;2&nbsp;3&nbsp;4<br>
 1&nbsp;&nbsp;2&nbsp;&nbsp;3&nbsp;&nbsp;&nbsp;4

renders as:

1 2 3 4
1  2  3   4

But since everything outside a <code> or <pre> block is rendered with a proportional-width font, you may find alignment across multiple lines to be tricky; in that case, using <code> blocks is probably your best bet.