As far as I know, there is no real evidence of this to date, but for purposes of argument, assume that we discover that Donald Trump Sr. was aware of, and even authorized, efforts by his associates to solicit information damaging to the Clinton campaign from individuals believed to be agents of the Russian government. Would that result in impeachment?
I doubt it. The “high crimes and misdemeanors” standard for impeachment in the Constitution doesn’t just apply to any old violation of the law, as Bill Clinton could tell you. I can’t imagine the GOP majorities in Congress pursuing impeachment unless there is also evidence of promises to change our foreign policy in relation to Russia in exchange for assistance with the campaign. That would effectively make Trump a Russian agent. Even Paul Ryan would have trouble with that one.
The truth is, the base might forgive him even for that. Sean Hannity would tell them that it is fake news, and they would believe it.