The Republican Party holds the presidency, controls both houses of Congress, and dominates legislatures and governorships in roughly two-thirds of America's 50 states. But that doesn't mean the GOP is healthy. Far from it.

Even aside from the stunning unpopularity of its signature policy initiatives and the record-high disapproval of its president, the GOP suffers from serious internal tensions. Indeed, if a new PRRI poll is to be believed, the most significant challenge of all might be the deep fractures within the party itself over President Trump. If the GOP isn't on the verge of disintegration, it may be just one potent primary challenge away from breaking into two.

According to the poll, only 63 percent of Republicans want Trump to be the party's presidential nominee in 2020, which is far below historic norms for a sitting president in his first term. On the other hand, those who do support the president are among those who are most attached to the Republican Party as an institution. Those Republicans also have more confidence in Trump than they do in the GOP overall.

In a word, the most fervent Republicans think the president, and not the party's leadership in Congress, exemplifies what the party should be and stand for.

But that is by no means a universally held view. When Never Trump Republicans (those who opposed him in 2016 and plan to again in 2020) are combined with Republicans leaning away from the president (those who favored him in the last race but have since soured on him for re-election), a total of 41 percent of the party can be described as essentially hostile to the president. (The discrepancy in the extent of Trump support across questions in the poll is a result of differently worded questions being addressed to different subgroups of respondents.)

That is at once a shockingly high and a shockingly low number. It's shockingly high because it means that two-fifths of the Republican electorate don't like the man who heads the party. That's an awful lot. But the number is shockingly low because it's nowhere near what we'd need to see for someone to launch a successful primary challenge to the president.

The key word is "successful."

Of course someone (hi Mitt!) could always launch such a bid in the hopes of torpedoing the president — that is, weakening him further as he heads into the general election, thereby helping to ensure his defeat at the hands of the Democrats. Leave aside the question of whether anyone in the party would choose to do this against a sitting president when no one dared to do so it in 2016 against a comparatively much weaker untested and patently unfit presidential candidate. The more pressing question is whether such a move would have any hope of laying the groundwork for a more appealing (non-Trumpian) version of the party to emerge in 2022 and 2024.

We have ample reason to doubt it.

When presidents face a primary challenge, it's usually from a restive faction further out from the center — think of Ted Kennedy challenging Jimmy Carter from the left in 1980 or Pat Buchanan taking on George H. W. Bush from the right in 1992. The goal is to make an ideological point — in the hope of steering the party away from compromise and conciliation down the road.

But in this case, the challenge would come from the more centrist faction of the party that was already defeated in the 2016 primaries. It would be a last gasp, a dying howl of the party's old guard, not a vision for where the party should turn next.

That's why such a primary challenge would be the harbinger of intra-party civil war, not a prelude to a vibrant, forward-looking takeover. Two-fifths of the GOP might be unhappy with Trump. But more than half of this group (or 23 percent of all Republicans) was happy enough with him to vote for him in the first place. A somewhat less volatile and incompetent cultural populist and nationalist could probably appeal to this group again. Only a mere 18 percent of the Republican Party is firmly Never Trump and thus likely to support returning the GOP to what it was before the Trumpening.

That means any attempt to take down Trump with a primary challenge will likely be interpreted by over four-fifths of the party — including, again, those who identify with it most strongly — as an act of disloyalty and self-sabotage by those who lost out the last time. (That an astonishing 11 percent of the Never Trumpers are Mormons and Mitt Romney's name keeps being floated as a primary challenger also raises the possibility of an added dimension of strife, along intra-religious lines, within the party.)

As we head through the midterms and onward to the 2020 primaries, there appear to be two options for the party: Either the generous deployment of negative partisanship (hatred of the Democrats) will succeed once again in papering over the GOP's deep and intractable differences — or else the party will begin to break apart.

A primary challenge would assure the latter. The absence of one might only delay it a little longer.