House Democrats are demanding that President Trump fire his senior aide Stephen Miller over leaked emails they say prove he is a "documented white nationalist."

The written request by 107 lawmakers is likely to be rejected by Trump, who has lashed out at Democratic lawmakers amid the second week of televised impeachment hearings.

Miller, a powerful Trump deputy who steers administration immigration policy, is well-known for preferring reduced immigration, but critics say the emails from 2015 and 2016 show how extreme his views are.

The emails "clearly establish that he is an avid white nationalist and conspiracy theorist," the House Democrats write. "These emails included material exposing Miller’s support of white supremacist ideology and literature, xenophobic conspiracy theories, as well as his promotion of white supremacist websites."

Emails from Miller to a former Breitbart News reporter were leaked first to the Southern Poverty Law Center. At the time, Miller worked for then-Alabama Sen. Jeff Sessions. Miller faces particular criticism for sending a link to the anti-immigration website Vdare.com and for mentioning the 1973 novel The Camp of the Saints, about a nonwhite immigrant invasion of Europe.

The House Democrats say there appears to be a connection between Miller's book reference and Trump administration policy.

"Mr. Miller’s documented hatred of Muslim immigrants shaped your Muslim ban, and sheds new light on your administration’s intent in writing that ban," they write. "Mr. Miller’s clear support for halting all immigration is evident in many forms, including your continued support for ending DACA as well as the increasing difficulty of obtaining asylum and visas across all categories. There is a clear line between Miller’s advocacy for books like Camp of the Saints — a novel celebrated by neo-Nazis for promoting the view of nonwhite immigrants as 'monsters' — and the Administration’s inhumane family separation policy, of which Miller was the primary architect."

White House representatives did not immediately respond to a request for comment.

Although no Republican signed the letter, Miller's views have put him at odds with some GOP lawmakers. Last year, he clashed with South Carolina Sen. Lindsey Graham on efforts to broker an immigration reform deal.

The letter-writing drive was led by eight House Democrats, including Rep. Ilhan Omar of Minnesota, a frequent Trump critic and target.

Miller is one of the longest-serving White House aides, often traveling with Trump and helping write his speeches. Occasionally he appears on TV or before reporters at the White House to defend Trump's policies. His longevity at the White House is seen in part as a testament to staying out of power struggles and administration intrigue that has doomed other senior aides. This year Miller led a White House drive to purge Department of Homeland Security leadership of officials deemed weak on pushing restrictions to asylum. Miller argued certain policies created a pull factor for Central American migrants.

[Opinion: It's high time for Trump to dump Stephen Miller]