It's often stated that no team has ever come back from a 3-0 deficit to win a seven game series. While this is true for the major leagues in the major sports, it's not true throughout professional sports.
The 1937 Newark lost three games at home to start the Little World
and then went to Columbus, and swept the Red Birds in four games there.
In game 1, the Bears blew a 3-1 lead, giving up 4 runs in the 7th in a 5-4 loss.
In game 2, the Bears came back from a 4-0 deficit entering the bottom of the 6th, forcing the game to extra innings in their 11 inning 5-4 loss.
In game 3, The Bears took a 3-2 lead after 1 inning, and held this score until allowing 2 runs in both the 7th and 8th innings of a 6-3 loss.
The Bears never trailed in Columbus, jumping out to leads in innings 3,2,1, and 2 on their way to 8-1,1-0,10-1, and 10-4 wins.
Newark demolished the International League that year, going 109-43, and
winning the pennant by 25.5 games.
From the Reach 1938 Baseball Guide:
"The first three games of the series were played in the Bears' stadium, all resulting in Columbus victories. When the teams moved to Columbus it seemed impossible for the Birds to be defeated, but they dropped four in a row. The loss of Captain Jimmy Jordan, who suffered a broken leg in a collision at second base, proved the first blow. Then both catchers, Jack Crouch and Frank Grube, split fingers that made it virtually impossible for them to throw to bases. Their inability made it possible for stolen bases to result in the winning run in two of the games staged in Columbus."
Further information about the Bears is at Minor League Baseball.com's Top 100 minor league teams site.
Closeness scores (sum of end-of-inning margins):
11 9 13 29 8 43 35