A wave of lawmakers from the state of Washington on Sunday called for an impeachment inquiry against President Trump, making it so that nearly half of the House Democratic Caucus now supports the move.

The call from the five Washington state Democrats - Reps. Derek Kilmer, Kim Schrier, Suzan DelBene and Denny Heck as well as Sen. Patty Murray - came four days after former special counsel Robert Mueller testified to Congress.

Although Mueller revealed little that wasn't already included in his 448-page report on Russian interference in the 2016 election, 11 lawmakers have moved to begin supporting an impeachment inquiry since the testimony.

The investigation did not find sufficient evidence to prove conspiracy between the Trump campaign and Russia during the election, and it neither implicated nor cleared Trump on the question of obstruction of justice.

Trump touted the hearings as a success, declaring the "phony cloud" cast by the investigation had been lifted and insisted "there was no defense to this ridiculous hoax, this witch hunt."

Over the weekend, however, he took aim at House Oversight and Reform Chairman Elijah Cummings (D-Md.), an African American lawmaker whose committee is conducting several investigations into the Trump administration. Trump's comments about Cummings and the city of Baltimore were widely condemned by Democrats as racist.

Under Cummings, the committee has voted to hold Attorney General William Barr and Commerce Secretary Wilbur Ross in contempt for defying subpoenas; heard testimony from former Trump attorney Michael Cohen; held a hearing on conditions at the southern border; and last week authorized a subpoena for official communications from senior White House advisers Ivanka Trump and Jared Kushner.

It marked the second time in three weeks that Trump targeted a prominent minority Democratic lawmaker and in many ways mirrored the way his attacks on Reps. Alexandria Ocasio-Cortez (D-N.Y.), Ilhan Omar (D-Minn.), Rashida Tlaib (D-Minn.) and Ayanna Pressley (D-Mass.) played out.

Another key committee leader, House Judiciary Committee Chairman Jerrold Nadler (D-N.Y.), on Sunday said that Trump "richly deserves impeachment" but stopped short of joining a growing call for House Democrats to begin a formal inquiry.

"My personal view is that [Trump] richly deserves impeachment. He has done many impeachable offenses. He's violated the laws six ways from Sunday," Nadler said on CNN's "State of the Union."

The four Washington state representatives, who all cited Mueller's report in their statements, bring the total number of House Democrats calling for impeachment proceedings up to 103, just 15 shy of a majority of the House Democratic Caucus.

Murray, the No. 3 Democrat in the Senate, said in a statement that "as we have learned more about the gravity of the potential threats to our democracy identified in Special Counsel Mueller's report, it has become clear the House should begin proceedings to determine whether the President's actions necessitate impeachment."

Democratic leadership has so far been hesitant, instead asking the caucus to focus on investigations and oversight.

House Speaker Nancy Pelosi (Calif.) said Friday that she has no problem with individual Democrats calling for impeachment despite her reservations about moving forward with the process.

"Their advocacy for impeachment only gives me leverage. I have no complaint with what they are doing," she said.