Treasury Secretary Steven Mnuchin on Monday rejected House Democrats’ request for President Donald Trump’s tax returns, failing for the third time to meet a congressional deadline to turn over the documents. The move raised the stakes in the fight between the administration and Congress over the returns, making an unprecedented legal battle to obtain them all but certain. The Treasury secretary told House Ways and Means Chairman Richard Neal, D-Mass., in a letter that his committee's request for the president's tax returns “lacks a legitimate legislative purpose.”