The 12th Amendment was needed because...

To prevent deadlocks from keeping the nation leaderless.

Explanation:

The Twelfth Amendment provided that if the House did not choose a President before March 4 (then the first day of a Presidential term), the individual elected Vice President would "act as President, as in the case of the death or other constitutional disability.

Hoping this helps :)

the main reason the us senate rejected the treaty of versailles was because "european nations wanted to punish germany"

d(:

me and mark as brainliest.