That investigation could end now. The House has issued multiple subpoenas, all of which Trump has publicly declared that he will defy.
That is obstruction of justice in the most obvious, glaring sense.
His lawyers’ pettifogging to the contrary, he has zero legal grounds on which to defy a subpoena from the House of Representatives.
The Supreme Court has declared, unanimously, in Nixon v. U.S., 506 U.S. 224 (1993), that it lacks the power to review a decision by the Senate about how to conduct an impeachment trial because the Constitution grants to it “the sole power to try all impeachments.” Similarly, it grants to the House “the sole power to impeach.” If the Supreme Court lacks the power to review decisions of a House of Congress in its decisions about how to conduct impeachments, certainly the executive also lacks that power. All the more so when the official at peril of impeachment is the same president. This is too obvious to admit of challenge.
The Supreme Court has also declared, again unanimously, that a categorical assertion of executive privilege may not permit a president to defy a subpoena lawfully issued. That case, U.S. v. Nixon (yes, amazing historical coincidence), 418 U.S. 683 (1974), involved the attempt by President Nixon to refuse to submit tapes and other documents to a federal judge in the trial of the Watergate burglars. The Court held that granting such a privilege to a president would entirely defeat the checking and balancing that is a key purpose of the separation of powers.
From these two decisions, the House is entirely justified in stating categorically that the so called president has already committed a high crime of the sort that directly implicates the peculiar powers of the president and thus deserves impeachment.
They have all they need.