I'm not familiar with Beautiful Soup but I assume that soup (in your code) is a text string. If I'm correct then you want to be using string replace methods:
str.replace(old, new[, count])
Return a copy of the string with all occurrences of substring old replaced by new. If the optional argument count is given, only the first count occurrences are replaced.
If you have to make sure that your 'Running' is not in the middle of a word (outrunning), or it case is unimportant, or if there are additional considerations then you may have to move up to the re (regular expression) module
re.sub - http://docs.python.org/py3k/library/re.html?highlight=re.#re.sub