What event made the Compromise of 1877 possible? O A. Democrats had gained enough power to get things they wanted
from Republicans.
B. Republicans had promised to remove federal troops once
Democrats had control in all southern states.
C. Republicans had lost interest in southern issues.
D. Democrats had won the presidency

The event of won presidency by the Democrats made  the Compromise of 1877 possible.

The Compromise of 1877 was a unwritten deal among the United States Congressmen which settled the disputed 1876 presidential election.

In the compromise, the Democrats controlled the House and this allowed the decision of the Electoral Commission to take effect.

Hence, the event of won presidency by the Democrats made  the Compromise of 1877 possible.

In conclusion, the Option D is correct.

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they united the colonies in their fight against the british.