What were main political issues of the Gilded Age (1877-1900)?

Probably the most important political issue of this period
was the issue of the gold standard versus free silver.  This pitted business interests
against farmers.  The farmers wanted silver money to be coined so that the value of the
dollar would decline and it would be easier for them to pay off their loans.  Business
interests wanted a strong and stable currency.  This issue played out over a number of
presidential elections.

A second important issue was the
issue of regulation of railroads and other major utilities.  This was another major
issue for populists.  The populists (mainly farmers) wanted the government to regulate
railroads because the farmers needed the railroads to get their crops to market. 
Because of this, the railroads could charge very high prices to farmers.  The farmers
felt that they were being unfairly exploited and wanted the government to prevent
this.

These were the two most important political issues of
the time you are asking about.