In an ad that ran over the summer, Mike Braun stood beside cardboard cutouts of his opponents in Indiana's Republican Senate primary, asking passersby whether they could tell the difference between the two men. No one could. It was, by the not very demanding standards of primary campaign commercials anyway, funny. It was also effective. Braun won the Republican nomination handily — thanks in part to an endorsement from President Trump — and is now polling about even with his opponent, the Democratic incumbent Sen. Joe Donnelly.

The question is whether the joke's now on Braun. There are few meaningful differences between his populist Republican campaign and the one being run by Donnelly, America's second most conservative Democrat. Both men support Trump's proposed border wall, a tough line on immigration, the renegotiation of NAFTA, gun rights, and increased defense spending. Their messaging style is almost identical. In a recent commercial, Donnelly denounces the anti-ICE rhetoric of "the radical left" and "socialists [who] want to turn health care over to the government." He ends by praising and even quoting Ronald Reagan. You could paste Braun's face on top of Donnelly's leather jacket and the spot would work just as well.

Even their baggage is the same. In a campaign in which the decline of manufacturing is the central economic issue, both candidates have drawn attention to how the other's respective family business has profited from outsourcing. The "o" word is one of the most toxic in the Hoosier vocabulary. What in other circumstances could open one man to charges of hypocrisy is effectively neutralized by the fact that neither of them quite practices what he preaches.

The only serious difference between the two campaigns is over the successful nomination of Justice Brett Kavanaugh to the Supreme Court. Donnelly's decision to vote against Kavanaugh surprised some observers, who thought that it might cost him and other red-state Democrats in November. In this case I am not so sure. For one thing, it was clear that Republicans had enough votes to confirm Trump's second high court nominee with or without Donnelly. He cannot be held responsible by Trump supporters for bringing down a judicial candidate who actually succeeded. Braun's hypotheticals about what he would have done instead had he been in office are doubly irrelevant — he was not, in fact, there, and if even he had been, it would not have made a difference to the outcome.

What Donnelly's vote bought him instead is the good will of party leadership and a significant boost in credibility with the part of the Democratic base whose turnout he needs to win in November. With the shrewdness that allows all purple-state moderates to survive politically, Donnelly understands the mood of the liberal grassroots. Activists care a hundred times more about anti-Trump turf war — and about the legality of abortion, the real battle for which our recurring controversies over judicial nominations are proxies — than they do about Donnelly's concrete views on various policy questions, such as the provision of medical care or trade. A "no" to Kavanaugh makes him a party man and even, as far as campus progressives in Bloomington are concerned, a token member of the #Resistance.

The genius of Donnelly's campaign is that it leaves Braun with almost no opportunities of distinguishing himself from his opponent. He cannot accuse the man who proudly announces his support for ICE and the long-fabled Mexican border wall, the straight-shooting family man who, as one liberal voice in the state put it, "typically sided with the all-or-nothing views of the gun lobby," of being some kind of Kamala Harris clone. Nor can he credibly harp on about Donnelly's ties to outsourcing. Every candidate running against an incumbent builds his case by arguing against the status quo. If Donnelly is the status quo, even Braun doesn't want to change it much.

Unfortunately for Donnelly, a brilliant campaign may not prove to be a winning one. Braun has been rising steadily in the polls since August, when he was down by 12 points. That lead has shrunk to less than 3 percent. FiveThirtyEight still gives Donnelly a nearly 80 percent chance of victory, for mystical anagogic reasons that will remain unknown if he wins and swept under the rug if Braun somehow pulls through.

Regardless of who wins in November, those of us with Hoosier acquaintances will be wondering how they made up their minds. A coin toss is not an unattractive approach to the democratic process.