>perl -wMstrict -le
"print '------ output ------';
 my $s = shift;
 print $s;
 my @chunks = split m{ (\s+ AND \s+) }xms, $s;
 @chunks = map { m{ \b OR \b }xms ? qq{($_)} : $_ } @chunks;
 print join '', @chunks;
"
"huckabee AND jfkadlsfj fdsfldfj06329 OR reagan AND OReilly  AND   clinton OR sebelius OR mccain"
------ output ------
huckabee AND jfkadlsfj fdsfldfj06329 OR reagan AND OReilly  AND   clinton OR sebelius OR mccain
huckabee AND (jfkadlsfj fdsfldfj06329 OR reagan) AND OReilly  AND   (clinton OR sebelius OR mccain)