President Donald Trump is accumulating primary challengers, which should make both Democrats and never-Trump Republicans happy. Prominent never-Trumpers, however, have balked at the campaign of Joe Walsh and seem at best lukewarm about the prospect of Mark Sanford entering the race. They shouldn't be.
History shows that presidents who face strong primary challenges go on to lose the general election. A president who has trouble uniting his own base, after all, is going to find it difficult to produce the turnout necessary to win. Primary battles can expose deep divisions that are difficult to heal even after the convention.
Some never-Trumpers worry that a primary challenge against Trump could morph into third-party campaign that would weaken the eventual Democratic nominee. It's hard to see how the math would work: The presidential race is, of course, a series of 50 statewide contests (plus the District of Columbia). In every instance, the winner is the one who takes a plurality of the votes. So in order to win any state, a hypothetical third-party candidate would have to take more votes from Democrats than from Trump. As Nate Silver has pointed out, socially liberal but fiscally conservative voters broke for Trump in 2016.
Given that, it's possible — perhaps even likely — that a centrist like former Starbucks Chairman Howard Schultz would end up taking more votes from Trump than from his Democratic rival. It's a virtual certainty that a populist like Walsh, or even a solid conservative like Sanford, would significantly cut into the Democratic margin. The only primary challenger with appeal to potential Democratic voters is former Massachusetts Governor William Weld.
All of this presumes that any of the primary candidates would mount third-party campaigns, something the Republican National Committee requires them to pledge not to do. Much more likely is that they end their bids in the primary.
What about the candidates themselves? None, of course, is ideal; no candidate ever is. And yet the more of them there are, the more likely it is that one of them will be taken seriously. The RNC is not inclined to sanction any debates against Trump right now, but if he had several legitimate challengers, it would face increasing pressure to allow them.
Weld, who represents the remaining liberal wing of the Republican Party, has polled in the double digits against Trump. Still, Fox News, the de facto gatekeeper for Republican presidential candidates, has so far given his candidacy little oxygen.
Walsh complicates that equation. He attacks Trump from the right. He's an experienced talk show host, and he fits right into the Fox News demographic. He also provides an angle for provocateurs like Ann Coulter to express their displeasure with the president. It can be difficult for moderates to remember, but despite his fiery rhetoric Trump has so far failed to actually deliver on his promises of decreasing immigration, building a wall or eliminating the trade deficit with China.
Sanford adds a further wrinkle. As a staunchly conservative former member of Congress and South Carolina governor, he would be a legitimate contender. His primary disqualification, a messy extramarital affair, is mitigated by Trump's own past.
Crucially, these three candidates themselves embody an important debate about where the Republican Party needs to go — after Trump. Weld represents old school supply-side Republicanism, which may be waning in popular support but remains influential in actual GOP politics. It's worth noting that the only major policy uniting the party in the Trump era is the 2017 tax cuts. Walsh represents the seemingly ascendant tide of populism. It gets a lot attention and Walsh will make himself heard, but it has not been able to unite the party elite. Sanford represents what remains the core of the GOP in the 21st century: social and fiscal conservativism.
The question is not so much whether one of these candidates can win; it's the future direction of the Republican Party. Republicans are going to continue to win elections, and eventually their party will stand for something more than Donald Trump. The sooner they figure out what that is, the better for their party — and, not incidentally, the nation.