my_str ='·in this match, dated may 1, 2013 (the "the match") is between brooklyn centenniel, resident of detroit, michigan ("champion") and kamil kubaru, the challenger from alexandria, virginia ("underdog").'

champion = re.findall(r'("champion"[^.]*.)', my_str)
print(champion)

>> ['"champion") and kamil kubaru, the challenger from alexandria, virginia ("underdog").']


underdog = re.findall(r'("underdog"[^.]*.)', my_str)
print(underdog)

>>['"underdog").']

brooklyn centenniel, resident of detroit, michigan