The cliché says it’s the Minister for Finance’s job to say no: to lobbyists, coalition partners, interest groups, semi states, protesters, government departments, and fellow TDs. Everyone wants something from the Minister for Finance (and more recently, the Minister for Public Expenditure and Reform). The temptation is to say yes. There are always urgent problems. Especially now, in 2020. And voters care mostly about the here and now.  The challenge for a budget minister is to know how much spending is too much. That’s hard because the rules of the game are constantly changing. Financial markets can be schizophrenic. In…