Win or lose, Rep. Beto O’Rourke, D-Texas, has some serious cajones. He is running against Sen. Ted Cruz, R-Texas, and running strongly, in a state where guns are regarded by many as a birthright — and he is advocating not just minor gun controls but a complete ban on the sale of semiautomatic assault rifles such as the AR-15. His sensible stance has been predictably attacked by Texas Republicans, who will use it to paint him as out of step with “Texas values.”

There is, on the surface, nothing surprising about the GOP tactics, since Republicans have long been known as the gun-rights party. But it wasn’t always thus. Republicans made the same transition on gun control as on environmentalism, civil rights, immigration, taxes and other issues — from moderate conservatism to far-right fanaticism. Therein lies a tragedy for the Republican Party — and for the republic.

The National Firearms Act of 1934, which imposed stringent regulations and taxes on the sale of machine guns, automatic weapons, and sawed-off shotguns and rifles, was so uncontroversial that it was passed by voice vote in both the House and Senate. The NRA, which in those days was concerned primarily with improving marksmanship, even supported the legislation. The Gun Control Act of 1968, passed after the assassinations of Robert F. Kennedy and the Rev. Martin Luther King Jr., further toughened regulation of the gun industry. It passed with roughly 70 percent support in both houses, and Republicans and Democrats backed it equally.

By the 1990s, following the NRA's transformation into a powerful gun lobby, opposition to gun control had become an article of Republican faith. But there was still some room for dissent. Former president Ronald Reagan's support ensured passage in 1993 of the Brady Law, which imposed a five-day waiting period on the sale of handguns by licensed dealers. It was named after his press secretary, Jim Brady, who had been gravely wounded with a cheap handgun known as a Saturday Night Special in the 1981 attempt on Reagan's life. Because of the Gipper's involvement, 31 percent of House Republicans and 36 percent of Senate Republicans supported the bill.

Reagan's support, even in retirement, also helped to pass a ban on the sale of assault weapons in 1994. But this time only 26 percent of House Republicans and 16 percent of Senate Republicans voted aye. That small gun-control caucus was composed of moderates, such as Rep. Robert Michel, R-Ill., and Sen. Bob Packwood, R-Ore., who were rapidly disappearing from GOP ranks. By the time the assault-rifle ban expired in 2004, congressional Republicans were determined to let it expire - and they did. President George W. Bush expressed willingness to sign a renewal but did not actively lobby for it.

No federal legislation toughening gun laws has been passed since 1994, largely because the GOP has become a wholly owned subsidiary of the gun lobby. Democrats, for their part, have varied in their enthusiasm for gun control; their support waned after the passage of the assault-weapons ban was blamed for costing them control of Congress in 1994. The Republican Party orthodoxy has become that anyone - no matter how demented or dangerous - who wants a military-grade weapon should be entitled to one. (The only real difference between an AR-15 and a military-issued M-4 or M-16 is that the latter can fire in "burst" mode, i.e., three shots per trigger pull, but in practice soldiers are taught to use semiautomatic mode, i.e., one shot per trigger pull.)

That obstinate attachment to weapons of war has survived one mass shooting after another: Santa Fe, Texas, 2018 (10 dead); Parkland, Florida, 2018 (17 dead); Sutherland Springs, Texas, 2017 (25 dead); Las Vegas, 2017 (58 dead); Orlando, Florida, 2016 (49 dead); San Bernardino, California, 2015 (14 killed); Newtown, Connecticut, 2012 (27 dead). It is no mere coincidence that so many mass shootings have occurred since the assault weapons ban expired, because so many of the shooters used assault weapons.

Economist Mark Gius of Quinnipiac University found that the federal assault weapons ban had little impact on the overall U.S. murder rate, which has been declining for years but is still much higher than in other Western countries. It did, however, have a "statistically significant" effect on the number of school shooting victims. "When the assault weapons ban, state or federal, was in effect, the number of school shooting victims was 54.4 percent less than (when it was not in effect)," he writes. A federal assault weapons ban would be even more beneficial if, unlike the 1994 legislation, it were not riddled with loopholes and if, as in Australia, it included a provision forcing existing gun owners to turn in their assault rifles.

But on gun control, as on so many other issues, Republicans today are immune to reason and at odds with their own history of moderation, because they regard an absolutist position as a political necessity. If O’Rourke manages to win - improbable but not impossible - his success could call that destructive assumption into question.

Max Boot | The Washington Post

Max Boot, a Washington Post columnist, is the Jeane J. Kirkpatrick senior fellow for national security studies at the Council on Foreign Relations and a global affairs analyst for CNN. He is the author of the forthcoming “The Corrosion of Conservatism: Why I Left the Right."