What tranformed u. s. politics in the 1920s

"A split in the Democratic Party" was one reason among the choices given in the question that transformed U.S. politics in the 1920s. . I hope that this is the answer that has come to help

the  seven  days  battles  were  a series of seven battles over seven  days from june 25 to july 1, 1862, near richmond, virginia,  during  the american civil war. the  seven  days ended with mcclellan's army in relative safety next to the james river, having suffered almost 16,000 casualtiesduring  the retreat.

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