Fair point! I am speaking to my beliefs here, based on my worldview and my sense of "how things work". There were no whistleblowers reporting on any of Obama's calls to foreign leaders in 2016 (at least any that were embraced by the MSM...), so there is no definitive proof. But the commission of the Steele Dossier is the salient example the Republicans are and will continue to use.
Would you also agree that Josh's extraordinary statement above that "No president has ever asked a foreign country to investigate one of his political opponents" needs a citation?