Bernie Sanders has bestowed his personal endorsement on just six congressional candidates in contested primaries so far this election cycle, and most of those have lost. But Sanders isn’t buying the idea that the lackluster record is any reflection on his clout.

“That’s a stupid argument,” the Vermont senator told NPR Thursday. Winning primaries, he argued, is secondary to the goals of encouraging more people to participate in the political process and fighting for a progressive policy agenda. On those fronts, he says he’s making significant progress.

“I [could] be 100 percent in terms of my endorsements,” he said. “All you’ve got to do is endorse establishment candidates who have a whole lot of money, who are 40 points ahead in the poll. You know what, you’ll come and say, ‘Bernie, you were 100-percent supportive of these candidates, they all won.’” Sanders said he’s instead mostly thrown his support behind underdogs. “The candidates that we support, by and large with few exceptions, are all candidates who are taking on the establishment, and are often outspent.”

That’s mostly accurate. The two Bernie-backed candidates who have prevailed in House primaries are proud progressives, but they are hardly status-quo-shaking outsiders. Rep. Nanette Barragán was the incumbent in her deep-blue district in California, and Jesús “Chuy” García was handpicked by the retiring congressman to replace him in a similarly deep-blue district in Illinois. Sanders’ endorsees have also won a handful of statewide races, including Georgia gubernatorial nominee Stacey Abrams, who also had the backing of a number of national Democrats, and Pennsylvania lieutenant gubernatorial nominee John Fetterman.

Bernie’s latest primary defeat, meanwhile, came this past Tuesday in Iowa, where his former state campaign coordinator, Pete D’Alessandro, finished a distant third in a three-way congressional primary despite Bernie stumping for him in person, on television, and via his email donor list. In that contest, D’Alessandro ran slightly to the left of his two rivals, but the ultimate nominee nonetheless advocated for things like a public option, all-day kindergarten, and a constitutional amendment to overturn Citizens United.

Other notable losses include: Marie Newman, a progressive who was unable to defeat a Blue Dog Democrat incumbent in Illinois despite the backing of a wide swath of the liberal groups.

Sanders may be a victim of his own success, at least when it comes to endorsements. Greg Edwards and Rich Lazer, both of whom came up short in far more wide-open contests in their respective Pennsylvania districts last month, were the most progressive candidates in their races, but each lost to a candidate with progressive bona fides of their own, including support for things like expanded health coverage and a higher minimum wage. Those, of course, were a couple of Sanders’ hallmarks during his surprisingly successful primary campaign in 2016.

Sanders appears to take the long view with his congressional picks too. “I hope they win,” he said of the candidates he endorses. “Maybe they don’t. But if you get 45 percent of the vote now, next time you may well win.”