As Clinton struggles, Obama keeps up the pressure. Not only is his campaign zeroing in on Republican candidate John McCain and behaving as if the Democratic race is just about over, but Obama has also made a key shift in framing the nomination contest. Obama and his advisers no longer emphasize his lead in total delegates over Clinton, which is a confusing mishmash. Instead, they're focused on an easy to comprehend concept: the dwindling number of delegates he needs to lock up a majority. Late last week, Obama press secretary Bill Burton announced that four more party leaders, all superdelegates, were endorsing the front-runner. Burton said that meant he needed only 169 more delegates for the nomination, neatly illustrating how close Obama is to locking things up.