It could prove interesting to discover the proportion of Republican voter that, whilst faithful to party, come what may, actually disapproves of Trump, the man. And by extension, whether loyalty to party extends even to times when that party goes against the particular voter's own beliefs.
Yes, indeed: the three significant policy initiatives of the Trump Administration that are genuinely Trumpian—more restrictive border controls, protectionist tariffs on imports, and an isolationist approach to foreign relations—are more closely aligned with national Democratic than Republican doctrine. (The fourth major policy initiative, an income tax reduction skewed to provide most of its benefit to businesses and wealthy individuals in order to encourage capital formation, is consistent with the views of traditional Republicans. However, it was the product of negotiation between Paul Ryan, then the Republican speaker of the House of Representatives,* and the anti-tax "Freedom Coalition" faction of his party; based on his claims that it was intended to benefit the middle class, it's not clear whether Trump ever actually understood the new tax provisions.)
But with respect to impeachment, I suspect what will determine whether Trump is removed from office will be the political calculation of the Republican members of the House of Representatives, which would vote whether to bring Trump to trial, and the Senate, where the trial would be conducted.** I wouldn't be surprised if a considerable number of the Republicans in both chambers would prefer to be running with someone other than Trump as their presidential candidate next year, but they're also leery of offending the Trump "base," which contains a high proportion of non-traditional Republican voters. The latter are highly motivated, and capable of threatening the careers of incumbent Republicans who they consider anti-Trump by challenging them in the intraparty state "primary" elections that will be held in the spring.
Timing will be important to these on-the-fence Republican members of Congress. If the votes in the House of Representatives (impeachment) and Senate (conviction) come after the primary election season, and if the evidence against Trump appears convincing, the persuadable Republicans may feel that removing him and selecting a different presidential candidate would both improve their own chances of being re-elected and of holding the White House for another four-year term. Especially if the Democrats appear on the way to selecting a presidential candidate from the left wing of their party, for example Senator Elizabeth Warren, a traditional Republican like Mitt Romney, senator from Utah and a former presidential candidate, would be able to run from the center and possibly secure a larger proportion of the critical suburban vote than Trump.
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*In the United States, the speaker of the House of Representatives is a party leader, not a neutral presiding officer of the chamber.
**The Democratic majority in the House of Representatives has enough votes to impeach Trump, assuming not too many of its members dissent. But the participation of a significant number of Republican representatives would no doubt increase the probability of conviction in the Senate. A two-thirds supermajority would be needed to remove Trump from office, which would require Republican votes.
