Who is Really Responsible for all the Spending?

Politicians campaign on promises. Promises to build a bridge. Promises to fix a road, build a new school, libraries, art museums, etc, etc. They listen to the wants and needs of their constituents and promise to bring home some federal pork and that is why the people in their state or district vote for them. They are keeping the promises that the voters are holding them to, hence all the overspending on the hill. Why do we blame the politicians for promising to haul home barrels of pork that the voters made them promise to bring home to their state or district in the first place? That is their job. So who is responsible for all the spending? Us or them?