How was Jackson's campaign approach different from his predecessors?

Many experts believe that Andrew Jackson's presidential campaign was the forerunner of the modern presidential campaign.
It represented the first time an outsider ran for the presidency. Jackson was not a member of the ruling elite. However, he was a hardscrabble fighter and a war hero. He served in the War of 1812 and won a decisive victory for the United States in the Battle of Horseshoe Bend.
Jackson initially ran for president in 1824. However, he did not win the electoral vote and so, did not ascend to the presidency. Jackson had always felt that the election was stolen from him, and he decried the prominent place the electoral college held in presidential elections. In the United States, a candidate must receive 270 electoral college votes to win the presidency. If no candidate receives 270 electoral votes or more (as it happened in 1824), the House of Representatives picks a president from 3 of the candidates who received the most electoral votes. You can find the provisions pertaining to such a situation in the 12th Amendment.
Those who rejected abolishing the electoral college maintained that it was unfair to use the popular vote to decide future presidential elections. They argued that the popular vote was mainly derived from large urban populations. Specifically, they were concerned that the voice of rural voters would be ignored if the electoral college was abolished. Today, the same arguments for or against the electoral college exist. Now, back to Andrew Jackson.
In 1824, Jackson and his supporters believed that John Quincy Adams and Henry Clay conspired to rob him of the presidency. Jackson (nicknamed Old Hickory) and his supporters eventually began a campaign to overturn public support for the electoral college. They argued that future presidencies should be decided by the popular vote, the first time such an argument had been made.
Their actions led to the formation of today's modern Democrat Party. Some historians maintain that the 1828 campaign also marked the first true mud-slinging campaign in American history. Both John Quincy Adams and Andrew Jackson engaged in mud-slinging. You can read about it from the link below.
So, the 1828 Jackson campaign marked the first time that a presidential candidate openly called for the electoral college to be abolished. It also marked the first time opposing candidates resorted to direct appeals to voters to win an election. Until Jackson, previous candidates relied on political organizations to get their messages across. In 1828, Jackson and his supporters held rallies and other public events to promote his candidacy (the precursor of modern presidential campaign rallies). They presented their case to the electorate and argued for the electoral college vote to be abolished.
https://www.britannica.com/event/United-States-presidential-election-of-1828

https://www.thoughtco.com/the-election-of-1828-1773861