The term pork barrel politics usually refers to spending which is intended to benefit constituents of a politician in return for their political support, either in the form of campaign contributions or votes.
Pork-barrel politics is the legislator's practice of slipping funding for a local project into a budget. The project may have nothing to do with the bill and may benefit only the legislator's home district. Before a bill gets to a vote, pork-barreling has often greatly inflated its costs through the addition of various legislators' pet projects.
In modern politics, pork-barreling and earmarking have become virtually synonymous. To be fair, one politician's pork-barrel politics is another's constituent service.
Alaska's proposed Gravina Island bridge and Boston's Big Dig are examples of pork barrel spending.
Attempts to control Pork Barrel Politics
The 2011 Bipartisan Control Act placed a moratorium on earmarks, which lasted in some form until 2018 when the Bipartisan Budget Act removed all restraints. Although plenty of earmarks got through during the moratorium years, but their numbers soared more than 13% after it was lifted.
The line-item veto, which was promoted as a pork-busting tool, was granted by Congress in 1995. President Bill Clinton liberally used his power to strike individual budget items, but as it turned out he would be its sole practitioner. In 1998, the line-item veto was ruled unconstitutional by the U.S. Supreme Court.