What were the strongest arguments for the extension of the right to vote in the 1830s? What were the arguments in the 1860s?

The growth of suffrage (the right to vote) was slow and unsteady in the United Kingdom. Two of the watershed moments in the expansion of the right to vote, though, came in the Reform Acts of 1832 and 1867. Both of them were backed by popular support that threatened to boil over if the right to vote was not expanded.
The arguments for expanding voting rights in England began in the 1600s after costly civil wars ended the absolute power of the monarchy. Voting, it was clear, was a better way of choosing leaders than fighting, and voting gave the public a greater say in the government above them. However, it was the French Revolution in the 1790s that spread the idea of suffrage still further, igniting public opinion in its favor.
In England, it was the death of King George IV in 1830—which dissolved Parliament and created a general election—that provided the much-needed opportunity to overhaul England’s election laws. The result was the Reform Act of 1832, which simplified the archaic way elections were held and also drastically reduced the amount of property that needed to be owned in order to be able to cast a vote. This spread the right to vote, placating the public’s demands.
The 1860s saw another surge in the public’s demand for the right to vote: the American Civil War ended with the abolition of slavery in the US, making citizens in England clamor for more rights of their own. At the time, despite the expansion of the right to vote from the 1832 Reform Act, only one in seven adult men could vote. Additionally, the industrial revolution had led lots of people to move from the countryside into the cities of England, changing how many people lived in certain counties and their proportional power in Parliament. The Reform Act of 1867 doubled the number of men who could vote in England by again lowering the amount of property they needed to own in order to vote and changed how many representatives certain areas could send, effectively redistributing seats among the country. This redistribution was intended to help the powerful Conservative Party.
In the end, then, the strongest arguments in favor of expanding the right to vote in England in the 1830s and 1860s were that the expansion of voting was needed to placate the public, build a nonviolent way of changing leadership, and solidify political power.