One reason Andrew Jackson was considered a champion of the "common man" was because he

Fought in the war of 1812.

Explanation:

Andrew Jackson was considered as a champion of the "common man" because he fought the war of 1812. He was the first president who comes from a poor family instead from a wealthy background. He fought in the American Revolution in the year 1812 and he was a commander during the battle of New Orleans in 1812 so that's why people considered him a champion of the common man.

-18 metres sorry if im wrong

i believe the answer is:

-   william jennings bryan is a democrat while mckinley was a republican

at that time, the segment of population that choose for democratic party were the voters with low economic background and vice versa

- william jennings has support of populists and wants to have inflation to farmers while mckinley has support of bankers and businessmen , doesn't want inflation

the fixed value of gold make the large business able to stack up their gold without   being worried that it would devaluated.

- william jennings supported the silver standard while mckinley supported the gold standard

according to jenning, using other metal beside gold could the poor people to have more purchasing power and them advance in the society.