We really don't know if Trump has done anything illegal. It is all assumptions. We know most Democrats hate the heck out of Trump and want him destroyed. That they have been trying to do this since the day after the election. We also know most Republicans love him. Your reference to Nixon, half of all Republicans thought he was railroaded out of office back in 1974. In 1974 Republicans only had 42 senators while the Democrats had 58. The Democrats held a 243-192 advantage in the house. Impeachment was a sure thing in the House, all it took was the defection of 9 Republican senators to vote guilty to reach the magic number of 67. Much easier to reach the 2/3rd number needed in the senate. Today it would require 20 GOP senate defections instead of 9. Even in 1974 I doubt back then the Democrats could have got 20 Republican senators to desert Nixon.
Also back in 1974, both political parties had their liberal and conservative wings. There wasn't the stark left/right or liberal/conservative divisions as today. The Republicans were big in the Northeast, the liberal Rockefeller Republicans, the Democrats had their solid conservative south. Straight party line votes never happened back then. There wasn't a huge cry for impeachment coming from the Democrats either right up to the day Nixon resigned. I think most Americans knew impeachment was a real possibility, but no huge outcry.
With both major political parties in armed camps over Trump, it might be a good idea to find out what independents think. After all they now make up 40-43% of the electorate today depending on the poll. Party breakdown is also different today than in 1974. In 1974 Democrats made up 44% of the electorate to the Republicans 24% with 31% being independents.
Trends in Party Identification, 1939-2014 | Pew Research Center
today it is 31% Democrats, 28% Republicans and 39% independents. The Democrats held a huge 20 point advantage over Republicans in 1974 vs. only 3 points today. Today it is a much more even fight both in numbers of party affiliation and in the senate where the trial would take place. Different make up of the political parties also. Both have become much more ideological and yes, highly more partisan.
But what do independents think of Mueller's investigation that the democrats put so much stock in? Question 21, Witch hunt or legitimate investigation. Do you think the FBI investigation of President Trump is a witch hunt or a legitimate investigation?
39% of independents state legit, 36% say witch hunt. Fairly even split. 24% answer not sure, undecided or just don't care.
You also have the very partisan numbers on job approval of Trump also. 8% of Democrats approve, 88% disapprove. With republicans it's 86% approve, 10% disapprove. Is approval of Trump and whether the Mueller investigation is legit or a witch hunt, purely, 100% partisan? Look at independents, 41% approve of Trump, 46% disapprove. Question 50 Trump Job Approval. Do you approve or disapprove of the way Donald Trump is handling his job as President? Again an almost fairly even split among the less to non-partisan, the non-affiliated.
It seems to me that this whole thing is partisanship driven. Opinion of trump is partisan based, witch hunt or legit, partisan based. Impeachment, partisan based. Heck, in today's political environment, everything is partisan based. Neither party puts country first, let's be honest about that.
Whether or not Trump committed a crime, an impeachable crime, we have to wait on Mueller's final report to be sure one way or the other. For impeachment to work, you have to have a good sized majority of independents for it. Especially in today's ultra high partisan political environment. If impeachment looks like a partisan political vendetta against Trump without hard proof that convinces independents of his guilt. Impeachment could make trump look like the victim, provoke sympathy for him, backfire big time on the democrats. Beware what you ask for, you might get it. Especially if independents aren't on board.