with both Baltimore and NYY losing today, it is 21 days in a row that they have been within 1 game of each other. Even before today, it was the longest stretch at the top of a division or league since 1951, I think I heard today.
The '78 Yankees and Red Sox were close for the last few weeks of the season...don't remember how long. Ended in a playoff when Catfish Hunter lost the last game of the regular season.