Bernie Sanders is far from the slickest presidential candidate, but he is clearly the most effective television advertiser in the 2016 race. Sanders’ campaign is responsible for the three most effective presidential campaign ads that have aired this year, and six of the 10 most effective, research conducted by the advertising measurement firm Ace Metrix indicates.

The top-ranked ad, “For Jobs, For Us,” received an Ace score of 570, more than 100 points higher than the norm for a political advertisement, which is 450. Ace Metrix calculated its scores by showing ads to a pool of 500 registered voters balanced for age, ethnicity and gender based on the U.S. Census. The viewers were asked to score each ad on five factors, including how watchable it is, and how well it caught their attention and persuaded them.

Since the beginning of the year, some 240 different presidential campaign have aired and about a third — 78 of them — were produced in support of candidates who are no longer in the race. Of the remaining two thirds, Ted Cruz’s campaign is responsible for 51 of them, far more than the ads produced by his opponents John Kasich (16 ads) and Donald Trump (seven ads). On the Democrats’ side, Sanders’ camp has produced 33 ads, slightly more than Hillary Clinton’s 27.

While most of the ads aired were produced to support candidates, a substantial number of them were produced to trash one candidate. Ace Metrix tracked 28 anti-Trump ads, which have been produced by several camps, including the conservative political action committees the American Future Fund and the Our Principles PAC. Ted Cruz’s campaign, Cruz for President, has also made a number of anti-Trump ads, as has New Day for America, a PAC that supports John Kasich.

Two of those spots made Ace Metrix’s top 10 list. One called “Bob,” about a man who claims he was swindled out of money he invested in one of Trump’s business ventures, received the fourth-highest score of any presidential candidate ad aired this year. Another, called “Quotes,” which consists of women reading out phrases or descriptions Trump has used in referring to women, received the ninth-highest.

Those two ads grabbed the highest attention scores among Ace’s panelists. But unlike the rest of the top 10 list, both registered relatively low-impact scores, a separate Ace-created metric meant to illustrate how much an ad will influence someone’s vote.

While the number of ads attacking Trump is notable, the spending by the groups that made them has been modest. Combined, all of the super PACs that have made anti-Trump ads have spent less than $1 million airing them nationally, according to data from iSpot.TV. That’s a drop in the bucket for an election cycle expected to see nearly $6 billion spent on TV advertising, according to Borrell Associates.

And while Sanders carefully cultivates an image of a candidate who relies on grassroots support of his egalitarian message, iSpot data shows his campaign has spent more on national TV airtime than any of his rivals.

This story has been updated to clarify the nature of the cited advertising spending.