“impeached and removed from office”.
Ever read Woodward and Bernstein’s The Final Days, about the end of the Nixon administration? As July turned to August, 1974, the REPUBLICANS in Washington were increasingly desperate to get rid of Nixon The enormous permanent black mark of a Republican being the first U.S. president in history to resign in disgrace was not an impediment–they just wanted him gone. House Republicans were moving inexorably towards impeachment, and senators such as Barry Goldwater, Hugh Scott, and Robert Griffin, all Republicans, had made it known in GOP circles that they would vote to convict and remove Nixon. His remaining in office was a bigger black mark than his removal.
At that time (93rd Congress) Democrats had a 56 to 42 majority in the Senate and 242 to 192 majority in the House.
A bit of a difference from today, wouldn’t you say?
So you’re arguing that the GOP, when in the minority, wasn’t concerned about this “enormous permanent black mark” but when in the majority they will be, even if that concern might cost them their majority? 
The GOP, when in deep minority, had no way of preventing the impeachment (to state the obvious).
Not impeachment, but he’ll resign on September 16, 2019.
The GOP had plenty enough votes to deny conviction in the Senate, if the GOP senators held together. (It takes two-thirds, or 67 votes, to convict and remove from office; as you correctly note, the Democrats were eleven votes short.)
Moreover, the House back then still had a number of southern Democrats from conservative districts that Nixon had carried easily in 1972, so the party was hardly unanimous in their opposition to Nixon. (Every southern delegation except Tennessee and Virginia was majority Democratic, in fact, even in states Nixon had carried twice.) It’s not implausible that Nixon could have held some of these southern Democrats on the House floor. )
I would also point out that two of the five articles of impeachment failed in the Judiciary Committee, because substantial numbers of Democrats joined the GOP in voting against them.
Tolerating a Trump presidency is more of a black mark than removing him (if they can establish grounds)
Jan . 20, 2017 !
From your lips to God’s ears!
UK/Irish bookies are forming a view:
Bookies offer ‘even odds’ for Donald Trump being impeached while US President
Certainly, if one looked at Bill Clinton and Donald Trump on both of their inauguration days, one would have selected Trump as the more likely to be impeached. If the House flips, it’s anyone’s guess, assuming Trump continues on the course he has taken so far. As I said earlier, I wouldn’t say 50/50, but I’d say it would be > 10%. Which is damn high for any president.