Why did roosevelt attempt to "pack" the supreme court? how might american
politics be different if he had succeeded?

Roosevelt to add more justices to the U.S. Supreme Court in order to obtain favorable rulings regarding New Deal legislation that the Court had ruled unconstitutional. The bill came to be known as Roosevelt's "court-packing plan”.

Explanation:

The main aim of the New Deal is to bring down the cut-throat competition in the industries and the role government to take equal responsibility in advocating for practicing fair practices and to control prices.

An agency has be formed that is called "The National Recovery Administration (NRA)" was a prime New Deal agency formed by U.S. President Franklin D Roosevelt in 1933.

Roosevelt's purpose was clear to form the ideological balance of the Court so that it would stop striking down his New Deal legislation and this was called Court-Packing Plan. As a result, the plan was widely and vehemently criticized.

"The National Industrial Recovery Act" of 1933 was declared to be unconstitutional in May 1935 because the court tribunal stated that the NIRA extended the lawmaking authorities to the NRA in violating the allocation of the constitution of such powers to Congress.

it's not the readmission

the answer is that the political parties encourage people to caste vote.