A politician can win a lot of votes by amassing money for local projects that his constituents care about. Spending money gathered from a large swath of society on a project benefiting a smaller group is known as pork barrel spending. What is a pork barrel and where did this term come to have political meaning?
Back before refrigerators, it was common to store pork in a brine solution in a barrel. A wealthy family would have much more pork in that barrel and so it is a marker of affluence. Pork barrel spending is a reference to slavery. This sinister metaphor compares senators anxious to get the money for their constituents to slaves who would rush pork barrels dropped off by the slave owners.
Other languages have different ways for expressing this political tradition. My favorite is from German which is “Kirchturmpolitik” meaning “church tower politics”. In other words, the politician is only concerned with what he can see from his village church tower.