On Tuesday, more than half of Alabama Republicans chose Roy Moore to be their nominee for the United States Senate. There’s no single word that can capture Moore without euphemism, so it would be better to read directly from his political rap sheet.

Moore has been in Alabama politics for more than two decades, mostly as a state Supreme Court justice. During that time, he has condemned gay marriage and called same-sex relations “a crime against nature, an inherent evil, and an act so heinous that it defies one’s ability to describe it.” He believes homosexuality could disqualify a parent from child custody, believes Sharia law is an imminent threat to American communities, and has been twice removed from the Alabama Supreme Court for disobeying federal orders.

If Alabama follows its recent voting history, Moore will soon have the honor of serving in the Senate. His prospective colleagues have little to say about his record. In fact, they claim they’ve never heard of him. “I don’t know anything about Roy Moore,” said Iowa Sen. Chuck Grassley to Politico. “If I’ve read anything he’s said, I wouldn’t have any recollection of it.” Georgia Sen. Johnny Isakson says he’s “never met the gentleman,” although he admits that “Being from Georgia, which is next to Alabama, I’ve heard his name in the Alabama Supreme Court.”

It’s not that Moore is the first politician of his ilk to serve in Congress, but that he’s emblematic of changes in American politics broadly and the Republican Party specifically that may make the political mainstream more fertile ground for his kind of fringe figure.

Typically, extremist figures like Moore find themselves in the House of Representatives: beneficiaries of low turnout, gerrymandering, and overall lack of attention to most congressional contests. It is unusual for someone with this history to find himself in federal statewide office. But then, at this moment, much about the Republican Party is unusual, especially its voters.

To start, its voters have come to represent a demographic minority: older, wealthier, and much whiter than the country at large. Of the nearly 63 million voters who backed Donald Trump in the 2016 election, roughly 52 million—or almost 83 percent of the total—were white. And since 2008, many of those voters who comprise the Republican base have grown increasingly untethered from mainstream politics.

Some of this is the fault of Republican leaders themselves, who responded to the moderately liberal Democratic Party of Barack Obama with massive resistance, tolerating (even stoking) any attack or slander against the Obama presidency, as long as it damaged and delegitimized his agenda and his party. Some is the fault of conservative media, which spreads conspiracies and thrives on the paranoia and anger it feeds to viewers. And some is an anti-establishment fury that has grown after each of the recent Republican victories, when conservative voters realize their leaders have made promises they could never deliver on in the first place.

The response of those voters has been to back people manifestly unsuited for public office, from Christine O’Donnell and Sharon Angle in 2010 to E.W Jackson in the 2013 Virginia race for lieutenant governor. Roy Moore is just the latest in this line of candidates. He’s not even the first this year: Virginia Republican Corey Stewart ran as a Confederate sympathizer and nearly won the party’s nomination for governor.

Which gets to a key difference between the Obama years and now. Back then, the larger political climate was hostile to these kinds of candidates. Now, one of them is president of the United States. Donald Trump is living evidence that Republican voters will carry these rabidly anti-establishment politicians to victory, especially in the absence of a strong Republican Party establishment that can exert its will on the nomination process.

Trump, or rather his victory, also represents the structural forces that allow Republican voters to support these unqualified candidates without meaningful consequences for the GOP itself. Trump is a president who lost the popular vote and won the Electoral College with razor-thin margins in key Midwest states. He did this on the strength of his support with white voters, especially older ones, who have grown more polarized and are concentrated in those states. Trump could finish his first term in the depths of unpopularity, but if white polarization continues to grow—and if the distribution of his votes in electorally valuable states holds steady—then he could still win re-election.

That dynamic, where the structure of American politics creates space for polarized white voters to successfully back right-wing extremists—exists at other levels of government too. The House of Representatives is the clearest example. By a margin of 6 percentage points, according to the latest poll from the Economist, most Americans want the Democratic Party to control the House after the 2018 elections. But to do that Democrats would have to win the overall popular vote by roughly 8 percentage points—a huge margin. Aggressive Republican gerrymandering and the geographical clustering of Democratic voters give the party a distinct disadvantage in congressional elections.

That disadvantage doesn’t exist in the Senate, but a related one does: Because the states have equal representation—two senators each—rural states are hugely overrepresented relative to those with larger, more dense populations. Even without white polarization (and the low midterm turnout of traditionally Democratic groups during midterm elections) this fact gives a huge advantage to the party that controls those rural areas. It, along with the Electoral College, is a recipe for what New York Times columnist Michelle Goldberg calls “minority rule,” where a minority of the voting public wins unified control of the federal government for structural reasons even if the overall majority of voters back the other party.

Add racial and ideological polarization to the mix, and you have in these states the recipe for iron-clad one party control that creates conditions for candidates like Roy Moore. Worse, there’s no countervailing force—no countervailing demographic—within the Republican Party to stop its voters from indulging their most radical impulses. Just the opposite; the influence of conservative media means those impulses are encouraged and rewarded.

None of this is impervious to change. A genuine electoral wave would dislodge Republicans and create the space for reform and moderation within the party. The defeat of a candidate like Moore—or in 2020, the president—might discourage GOP voters from taking this path again. But for now, the most likely outcome is that other states will see their own Moore-like figures fueled by a Republican voting base that has taken its anti-establishment attitudes to an almost nihilistic extreme.

Republicans have won substantial power at every level of government, but far from tempering their impulses, that power has set them loose, free to wreak havoc on both themselves and the rest of the country.