The full House of Representatives will vote this week on the impeachment inquiry into President Donald Trump, addressing the White House argument that the probe has been illegitimate.

Democratic House Speaker Nancy Pelosi has scheduled a vote for Thursday, saying in a letter to fellow representatives that she wants to “eliminate any doubt” about the process.

Pelosi says the impeachment inquiry resolution will “affirm the ongoing and existing investigation … establish the procedures for hearings that are open to the American people … outlines procedures to transfer evidence to the Judiciary Committee … and sets forth due process rights for the president and his counsel.”

Trump and his Republican supporters have called the impeachment probe illegitimate because it is being held behind closed doors and the full House never voted for it. Pelosi says that argument “has no merit.”

There is no law saying the entire House has to approve an investigation and the majority party in control — currently the Democrats — set out the rules for an impeachment process.

Kupperman lawsuit

Meanwhile Monday, a former White House national security aide balked at testifying before the House committees.

Former Deputy National Security Adviser Charles Kupperman listened in on the July 25 call in which Trump pushed Ukrainian President Volodymyr Zelenskiy for “a favor.” Trump urged Zelenskiy to investigate alleged Ukrainian meddling on behalf of Democrats in the 2016 U.S. election and allegations of corruption by 2020 Democratic presidential candidate Joe Biden and his son, Hunter, who worked for a Ukrainian natural gas company.

When the White House ordered Kupperman to ignore the House subpoena, Kupperman filed a lawsuit Friday asking a judge to decide whose demand he should honor — the congressional subpoena or the White House.

House Democrats sent Kupperman’s lawyer, Charles Cooper, a letter over the weekend contending that the lawsuit lacked merit and had been coordinated with the White House. Cooper said the lawsuit had not been “even discussed” with the White House.

“It would not be appropriate for a private citizen like Dr. Kupperman to unilaterally resolve this momentous constitutional dispute between the two political branches of our government,” Cooper responded.

Intelligence Committee Chairman Adam Schiff calls White House efforts to stop Kupperman’s testimony another example of Trump’s obstruction of justice and another possible reason to draw up articles of impeachment.

Phone call

Democrats are investigating whether Trump withheld badly needed aid to Ukraine in exchange for Zelinskiy’s public promise to investigate Democrats and the Bidens.

Trump insists there was no quid pro quo between him and Ukraine and has called his telephone call with Zelenskiy “perfect.”

But U.S. Ambassador to Ukraine William Taylor testified last week the release of $391 million in U.S. military aid to Ukraine was directly linked to its willingness to open the U.S.-related political investigations Trump wanted.

Trump alleges that when Biden was U.S. vice president, he threatened to hold up loan guarantees to Ukraine unless a prosecutor stopped a corruption investigation into the gas company where Hunter Biden worked.

No evidence of wrongdoing by the Bidens has surfaced, and the allegations of Ukrainian meddling in the 2016 U.S. presidential election was based on a debunked conspiracy theory.