Former Rep. Tom Coleman (R-Mo.) has penned a blistering op-ed calling for the impeachment of “illegitimate” President Donald Trump.

Coleman, in his piece for The Kansas City Star published Thursday titled “Trump, Pence are illegitimate. Impeach them,” argued that if Trump was impeached, then Vice President Mike Pence should resign as otherwise “the lingering stench of corruption” would trail his administration.

Special counsel Robert Mueller’s report, Coleman wrote, showed Trump and members of his team had “on multiple occasions welcomed Russian interference on his behalf during the 2016 presidential campaign.” Therefore, Coleman reasoned, “the president’s election victory brought forth nothing less than an illegitimate president.”

Coleman, who has criticized Trump in the past and opposed his candidacy, was voted out of Congress after 17 years in 1993.

He noted in his op-ed that House Democrats were divided over whether to begin impeachment proceedings. But “critical times require exceptional leadership,” he wrote, suggesting the “only viable option available” is for the Democratic-controlled House “to open its own investigation, hold public hearings and then determine if they should pursue removal of the president through impeachment.”

“The public would conclude Democrats are no better than the Republicans who have enabled Trump for the past two years” if they did not move to impeach him, Coleman wrote.

He concluded with this warning:

It could hand Trump a second term. Failure to pursue impeachment is to condone wrongdoing. To condone wrongdoing is to encourage more of it. To encourage wrongdoing is to give up on the rule of law and our democracy. To give up on the rule of law and democracy invites autocracy and eventually dictatorship. History has taught us this outcome. In my lifetime, it has occurred in other places including the Soviet Union and Germany, as well as in Russia and Venezuela today.

Coleman in February joined 25 other previous GOP members of Congress in calling for the termination of Trump’s declaration of a national emergency to fund his promised wall on the U.S.-Mexico border.

In October 2016, he signed an open letter with 29 other GOP ex-lawmakers calling Trump an unacceptable candidate for the presidency.

Rep. Justin Amash (R-Mich) last weekend became the first current Republican member of Congress to call for Trump’s impeachment.

Read Coleman’s full op-ed in The Kansas City Star here.