During this tax season, U.S. Rep. Ben Ray Luján knows what it's like to feel the pinch of the Internal Revenue Service. Luján last month discovered that his campaign had underpaid payroll taxes for his campaign staff last year and owed the government more than $54,000 — including $13,627 in penalties and interest. His late payments to the IRS are listed on the freshman congressman's most recent campaign finance report — filed coincidentally on Wednesday, which also was the deadline for filing federal income-tax returns. His biggest contributors in the report were national labor unions. The International Brotherhood of Electrical...