A super PAC supporting Wisconsin Gov. Scott Walker's bid for the Republican presidential nomination released this ad as part of a series airing in Iowa until the February caucuses. (The Unintimidated PAC)

The first TV commercial promoting Scott Walker’s campaign for president looks like the product of a brainstorming session at Walker headquarters: flashes of the angry liberal protests that made him a national conservative hero, followed by Walker himself, sleeves rolled up, shaking hands and giving a speech.

But the ad — which started running in Iowa this week as part of a planned five-month, nearly $7 million campaign — was created by Unintimidated PAC, an organization barred by law from coordinating on strategy with the Wisconsin Republican governor since his campaign launch in July.

Unintimidated is one of about a dozen well-funded super PACs poised to dominate the airwaves this fall like never before. Of the approximately $77 million worth of airtime reserved by Republicans for the post-Labor Day sprint toward the first four primaries early next year, about $62 million is from super PACs, according to a Washington Post analysis of data provided by people familiar with the ad buys.

Television is still the medium of choice for candidates and the increasingly influential super PACs, but there are growing questions about the effectiveness of such efforts. First-time candidates Donald Trump and Ben Carson have skyrocketed to the top of the polls without making huge TV buys, while hopefuls backed by advertising, including Democrat Hillary Rodham Clinton, have fallen.

“We’re seeing an upending of what we have seen in recent presidential election cycles in the identity of the advertisers, in the amount of money going on the air at this particular time and in the approach taken toward the advertising,” said Elizabeth Wilner, senior vice president for political advertising at Kantar, a firm that closely tracks ads.

Wilner projected that more than half of all ad spending on federal races this election cycle will come from outside groups, including super PACs — up from about 40 percent in the 2012 campaign. So far, outside groups have accounted for nearly 80 percent of political TV ad spending, according to Wilner.

The unprecedented infusion of outside money arms candidates with powerful allies that are exempt from the fundraising limits the contenders face. But super PACs are also prohibited from directly coordinating with campaigns, raising the risk that they will cloud, rather than complement, their preferred candidates’ messages.

The biggest buyer on the Republican side so far is Right to Rise, a super PAC backing former Florida governor Jeb Bush that has reserved about $21 million for TV ads in Iowa, New Hampshire and South Carolina in the coming months.

Like most super PACs, it is led by a strategist who knows its favored candidate well: Mike Murphy, a longtime Bush hand. Unintimidated PAC is helmed by Keith Gilkes, Walker’s former chief of staff and campaign manager.

A big question facing Right to Rise is if and when it will attack Trump, the brash mogul and clear GOP front-runner. Although Trump and his allies have yet to reserve any airtime, he doesn’t appear to need it right now.

There has been pressure from some in the party to take on Trump more aggressively. But strategists tracking the race expect the first wave of super PAC ads to be mostly positive.

Keep the Promise I, a super PAC backing Sen. Ted Cruz (R-Tex.), plans to air a positive spot in Iowa during Saturday’s Iowa-Iowa State football game. GOP groups and candidates have reserved more than $25 million for fall and winter ads in the state, home to the first-in-the-nation caucuses.

The pro-Walker Iowa commercial is part of a broader $16 million investment to boost the governor’s image there and in New Hampshire, Nevada and South Carolina. Conservative Solutions PAC, backing Sen. Marco Rubio (R-Fla.), has reserved more than $10 million in ads in Iowa, New Hampshire and South Carolina beginning late this year, a wager that he will surge just before voting begins.

People familiar with advertising buys who provided information for this article did so on the condition of anonymity to offer a candid glimpse of the strategies of a number of GOP campaigns and super PACs.

Candidates’ ad spending can go further than that of super PACs; by law, candidates must be offered the lowest unit rates for the final few weeks before a primary. Bush hit the airwaves in New Hampshire this week, and Rubio has reserved substantial airtime beginning later this year.

Super PACs backing GOP long shots such as Bobby Jindal, Chris Christie, Rick Perry and John Kasich started airing ads even before Labor Day — a reflection of the intense competition to poll well enough to secure a spot in the top-tier primary debates. But few of those candidates have managed to gain momentum. The limits of super PAC advertising were made clear Friday when Perry dropped out of the race.

One exception is Kasich, the Ohio governor, who has moved into second place in New Hampshire polls.

And then there are Carson and Trump, running nontraditional, outsider campaigns that don’t rely on paid ads. Carson, a retired surgeon, has aired some TV spots but hasn’t signaled that he is preparing to blanket the airwaves this fall. Trump has benefited from constant free media attention.

“It matters a lot, but it’s not sexy like it was in the past. It gets drowned out,” Hogan Gidley, an adviser to GOP candidate Mike Huckabee, said of TV advertising.

Super PACs can raise unlimited money, but they face a common challenge. Under rules approved in 2010, a candidate for federal office cannot coordinate his or her paid communications with an independent group.

“The trick to super PACs is trying to anticipate your needs when you can still legally film your candidate,” said veteran admaker Fred Davis, who works for New Day for America, a pro-Kasich super PAC. Davis — who said he met Kasich just three months ago — called making super PAC ads a “tough long-term-thinking challenge.”

Kasich hit the airwaves this summer before he officially announced his candidacy, a period when his political operation was not subject to the same separation rules that apply now.

The rules do not ban coordination in general. Strategists on both sides can talk to one another directly, as long as they do not discuss campaign strategy.

There are work-arounds. Ahead of the first Republican debate this year, Bush’s campaign posted pages on his Web site with negative information about his opponents, then took them down once they attracted media attention. Such pages could be used to telegraph strategy or to signal what a campaign would like to see from an allied super PAC. It’s been done before.

And groups in need of fresh candidate footage need not worry. In 2014, the campaign of Sen. Mitch McConnell (R-Ky.) posted a clip reel on his YouTube page that an outside group later used to make a positive TV ad about him.

The race to scoop up pricey commercial time reaffirms TV’s central position in the 2016 campaign. Strategists say that even though many viewers record their favorite programs and skip the commercials, TV ads still capture the attention of viewers in ways other outreach doesn’t — at least not yet.

“Despite the allure of digital media, things like banner ads and search advertising don’t do as good a job as television commercials persuading the electorate to like or dislike a candidate or a particular issue,” says a report on 2016 campaign spending by Borrell Associates, which tracks advertising trends.

Borrell also projects that digital-media spending will top $1 billion for the first time in the 2016 contest. But the ad wars likely to define the race for the Republican nomination are playing out on televisions in cities such as Des Moines, Manchester, N.H., and Charleston, S.C.

“The primary and caucus process is about hunting ducks where the ducks are,” said longtime Republican strategist Scott Reed. “It’s not about moving national numbers.”

Matea Gold and Philip Rucker contributed to this report.