There’s a reason the early part of the presidential nomination contest is called the invisible primary: There are no television ads yet. Voters in key states should enjoy the lull while it lasts, which could be until summer or maybe even longer.

Four years ago, the first Republican presidential campaign ad appeared July 5. That’s when Tim Pawlenty, the former Minnesota governor, aired his first commercial for Iowa voters, according to broadcast advertising data tracked by Kantar Media and compiled by Deep Root Analytics, a Republican television advertising targeting company.

Michele Bachmann and Ron Paul followed soon after, but most of the field waited much longer. Mitt Romney, who eventually won the nomination, didn’t air his campaign’s first TV ad until Nov. 22, 2011, a good six weeks before the Iowa caucuses kicked off the formal primary season. (The data do not include cable or satellite TV advertising, which are not reported to the Federal Communications Commission.)

Political ads might not start running until later in this election cycle. The main reason the candidates may wait is simple: super PACs. Most of the early ads four years ago came from the campaigns, not from affiliated political action committees. Only a few of the 2012 candidates had affiliated super PACs; now most serious candidates will.

Because super PACs can raise any amount of money from donors while contributions to campaign committees are capped at $2,700 per person for the primary election, it can be easier to raise the money to pay for expensive TV ads via the super PACs. A round of TV advertising could be paid for by a few donors, leaving the candidate’s campaign free to spend its money on other activities – or to bank as much of the money as possible until later in the year. That might mean earlier ads will come from super PACs, while candidate ads happen later.

This is a big change from the last fully open presidential contest eight years ago, before super PACs existed. By the end of March 2007, Barack Obama had raised more than $25 million for his campaign, while Romney had raised almost $21 million. (John McCain, the eventual Republican nominee, did not start raising money until April of that year.) This year, none of the higher-profile politicians have even filed a statement of candidacy with the Federal Election Commission, let alone formally created a campaign committee.

The timeline could still shrink. In the 2012 race, most super PAC spending financed negative messages about other candidates. A significant amount of money will be spent when there is a clear leader to attack, but the Republicans don’t have that yet. The Democrats appear to have only one strong candidate so far, Hillary Clinton. It’s more likely that some Republican super PACs will air ads opposing Clinton. The lack of competition on the Democratic side could mean a longer wait for ads from Clinton, too.

The need for money to respond on television to attacks is part of what is driving fundraising for super PACs and other affiliated groups long before candidates actually register official committees. This part of the invisible primary – when candidates are as likely to appear before donors as voters – has two goals: gaining large donations and commitments to raise more.

Of course, you may never even see these ads. When the TV commercials do begin, even well-funded operations are likely to concentrate their messages on the states that hold their nominating contests first, particularly Iowa and South Carolina. The Iowa media markets of Des Moines, Cedar Rapids and Sioux City were the top three during the Republican primary in 2012, followed by the South Carolina markets of Greenville, Charleston and Columbia.

The sheer number of advertisements devoted to those states dwarfed those of larger markets in Florida and other states that held nominating votes early in the process. There were nearly 8,000 broadcast TV ads in the Des Moines market during the Republican primary; the Tampa market saw 5,400. (Owing to Romney’s popularity in New Hampshire, that state’s media markets were not among the top targets for the 2012 Republican primary, but that could change this time around.)

Although you may not see the ads on television, you might well see the ads online. In this current period of TV silence, campaign organizations are building an email list that can be used to raise money and target voters.

A committee formed by Scott Walker, the Wisconsin governor, has placed display ads on the websites of Fox News, The Daily Caller and other conservative outlets directing users to a page that asks for their name, email and address, according to Adomic, a California company that tracks digital ads. The leadership PAC of Chris Christie, the New Jersey governor, has also been buying ads on sites such as the Drudge Report. Potential candidates like Rand Paul, the Kentucky senator, and Jeb Bush, the former Florida governor, are posting messages to social media to help increase their reach and to identify supporters.

Derek Willis, New York Times