modifying search operands

Currently search results come up in relation to exact phrases only.

For instance if I type “george bush” into the search box, a post that just has the word “bush” in it, but NOT “george” won’t show up.

I would like to make the search look for “george” OR “bush”, not “george” AND “bush” (how it currently is).

Anyone know how to modify the search query to do this?

Thanks!