Is this impeachment constitutional? The White House doesn't think so

The White House has declared it won’t cooperate with the House Democrats’ impeachment inquiry. This shouldn’t come as a surprise to anyone who’s been paying attention to the political drama of the past year. Administration officials have stonewalled just about every one of the Democrats’ investigations over the past year. Why should this one be any different?

The reasoning for the president’s refusal, however, is a legal and constitutional head-scratcher. In a scathing 8-page letter to House Democrats, Trump’s counsel declared the impeachment inquiry a “highly partisan and unconstitutional effort” that attempts to “overturn the results of the 2016 election and deprive the American people of the president they have freely chosen.”