Senator Mitch McConnell, the Republican leader, has told associates that he believes President Trump committed impeachable offenses and that he is pleased that Democrats are moving to impeach him, believing that it will make it easier to purge him from the party, according to people familiar with his thinking. The House is voting on Wednesday to formally charge Mr. Trump with inciting violence against the country. At the same time, Representative Kevin McCarthy of California, the minority leader and one of Mr. Trump’s most steadfast allies in Congress, has asked other Republicans whether he should call on Mr. Trump to...