In a two-part article published late last week, longtime conservative direct mail entrepreneur Richard Viguerie warned that Libertarian candidates are on the verge of setting back the cause of liberty by contributing to the defeat of Republicans on Election Day. "The peculiar tendency for libertarians and constitutionalists to turn on anyone who works to change the Republican Party from within," Viguerie wrote, "has reared its ugly head again in this year's life or death struggle for control of Congress and key state Governorships."

Of the races for U.S. Senate—currently balancing on a 51–49 knife's edge favoring the GOP—that are most susceptible to Libertarian spoilage, Viguerie contended, "Indiana may be the most noteworthy."

As we have noted here, the Libertarians' nominee in that race, Lucy Brenton, has been consistently polling the second-highest of all 17 Libertarian Senate candidates, behind New Mexico's Gary Johnson (who on Monday was buffeted by an unhappy new Emerson poll putting him at 18 percent, well behind Republican Mick Rich's 32 percent, let alone incumbent Democrat Martin Heinrich's 48 percent).

In the six independent surveys that have included Brenton as an option, she's averaging 5.8 percent, far outpacing the difference between incumbent Democrat Joe Donnelly (43 percent) and GOP challenger Mike Braun (42.3 percent). She won 5.5 percent of the vote running for Senate in 2016, and will be appearing tonight in the second and final candidate debate.

Brenton is also appearing in a new Indiana Democratic Party mailer aimed at conservative voters to talk them out of voting Republican, according to the Indianapolis Star:

The words "Looking for a candidate who will really lower your taxes?" appear on the front of the flier. On the back, the mailer says that Brenton "is an anti-tax conservative" while Braun "raised Indiana taxes 159 times." Donnelly isn't mentioned.

"I am grateful for the free publicity highlighting my tax stance, but think it will backfire," Brenton told the Star. "Many Democrats are Constitution loving, fiscally conservative voters and my message resonates with them, too. Ultimately, how well they targeted the addresses will determine which voters learn that they have a choice in this race that demands all of their freedoms, all of the time."

It is unclear how Brenton's campaign is affecting the two-party race. In the only survey that asked respondents both with and without the Libertarian's name, the net effect of her inclusion was that Donnelly's lead shrank from six percentage points to three. In the Star article, Purdue political science professor Andy Downs says that, "The conventional wisdom is that Libertarians take votes away from Republican candidates. The idea being that the focus is on fiscal issues….However, Lucy Brenton has done well among folks who are traditionally Democratic voters as well."

I asked Brenton a month ago at the Texas Tribune Festival to theorize why she might be pulling more Democratic votes than Republican. Her answer:

[Donnelly] is widely known for crossing the aisle, advocating for Trump's wall, and would likely vote for [Supreme Court nominee Brett] Kavanaugh (note: days later he did not), but he's afraid to, so they're just trying to kick that can just a little bit further, a few more weeks. So he's a Democrat that, in a Republican state, does the smart thing of often voting with Republicans. My Republican opponent bought the election, the primary, against two very hated Republican contenders. But the point is that this guy was actually a Democrat for many, many years, voted Democrat in his local elections, and so people see him as a Democrat. So in my race, I'm really against two Democrats. So I'm taking votes, I'm spoiling, the more Democrat of the two, the incumbent, because he's the one who has advocated for medicinal marijuana, reluctantly. He is the one who's changed his position on gay marriage, reluctantly. But because I'm more on the side of freedom for the people who want that type of social freedom, those are the ones who are more likely to vote for me, because they're like, "You know what? He's just not going far enough. We want all of our freedoms all the time. The only person that's promised to do that for us is Lucy."

As a general principle, the "spoiler" charge rests on the assumption that the votes of a third-party candidate belong inherently to one of the other two. This is the case neither in principle nor practice: Exit polls consistently show that more than half of Libertarian voters would rather not vote than go D or R. The remaining minority is usually split one way or the other, depending on the characteristics of the race.

Still, here come the headlines: "Polls show Lucy Brenton as potential 'spoiler' in Indiana Senate race," "Libertarian candidate threatens to spoil Indiana Senate race," and "Will Libertarian Sink Republican in Indiana Senate Race?" If Brenton performs well at tonight's debate, and the Senate majority hangs on the balance of Indiana, this may be the race that Republicans or Democrats get most mad at.