Democrats already are moving to impeach Trump on the Ukraine matter. House Speaker Nancy Pelosi and others have told fellow Democrats to focus on Ukraine instead of on Russia conspiracy or obstruction, which led to more than two years of investigation. One reason for this is that Trump would be able to call his own witnesses during a Senate trial, particularly with a Republican majority dictating the rules. If the Russia investigation winds up as part of an impeachment trial, then Trump would be able to use these reports and earlier disclosures to place the conduct of the Obama administration under the spotlight before the public.
Trump would have plenty to work with in such a trial. The original focus was on his campaign aide Carter Page, who ultimately was not indicted on any crime. Mueller could not find a single crime by George Papadopoulos other than a marginal false statement that led to a whole 12 days in jail. Mueller ultimately found that no Trump official knowingly dealt with Russian hackers or trolls. If Durham finds irregularities and improper conduct in the Russia investigation, it will reinforce the claim by Trump that his campaign was improperly targeted by hostile FBI officials.
Even worse is there could be a one two punch coming on the Russia investigation. Justice Department Inspector General Michael Horowitz is said to be close to releasing his report on the secret surveillance targeting Trump officials. The report is expected to be both comprehensive and damaging for many involved in the start of that investigation. Durham and Horowitz will not be easily dismissed. Both are widely respected and are working with career investigators. If either finds improper conduct, it could reinforce the position of Republicans and moderate Democrats in voting against the impeachment or removal of Trump, who strongly maintains that the Obama administration not only improperly targeted his campaign for investigation but proved lax in investigating allegations against Democrats ranging from Hillary Clinton to Joe Biden.
Convicting a president in an impeachment trial requires evidence and clarity. Even if Democrats only proceed on the Ukraine call, Trump will be able to claim that he sought evidence tied to the Russia investigation to assist Horowitz and Durham in their own investigations. He will be able to call witnesses like Hunter Biden on his business dealings in Ukraine while his father handed out more than a billion dollars in aid.
It is doubtful that Democrats could resist references to the Russia investigation in an impeachment trial, which would trip the wire for Trump to bring in countervailing evidence from the Horowitz or Durham reports.