AP Photo/Robert F. Bukaty

Political advertising on television is expected to jump 16 percent to a record $4.4 billion in the 2016 presidential cycle compared to four years ago, showing a continued belief by candidates that broadcast and cable TV is still the best way to reach voters, according to a Monday report from Kantar Media research.

Since the Supreme Court's Citizens United v. FEC decision in 2010 opened the way for unlimited spending by corporations and unions, analysts say television airwaves in primary and key battleground states have been seeing sharp growth in revenues from political ads. Already Democratic candidate Hillary Clinton has reserved $8 million in TV advertising that could begin as early as November.

The desire to reach TV eyeballs may seem like a contradiction given that a growing number of people are cutting the cord on traditional television and network ratings have been on the decline -- some of the ratings of the networks owned by Viacom, such as Comedy Central and MTV, are down double digits over the last year. Television viewing by 18- to 34-year-olds was down 17 percent in the first quarter compared to the same period in 2014, according to Nielsen.

But one thing that hasn't changed yet is the fact the most reliable voters tend to be older and are still turning mainly to traditional TV for their news and entertainment, especially shows such as Wheel of Fortune or the local evening newscasts.

And even as the campaign staffs of Republican and Democratic candidates experiment with new social media platforms such as Snapchat and Periscope, they still see TV as the most effective  medium for promotion.

"It's a simple truth that  people who watch local news tend to be voters," said Mark Fratrik, a senior vice president of research firm BIA/Kelsey.

The rise has been steady: Total political ad spending in 2012 was $3.8 billion and in 2008 it was $2.75 billion.

Report author Elizabeth Wilner, who heads Kantar Media's Campaign Media and Advertising Group, attributed the rise in political ad dollars in part to the Supreme Court's Citizens United ruling. That decision made it easier for outside groups to collect and spend unlimited amounts of money for candidates.

"Spotting the impact of Citizens United on congressional election spending is like spotting the Great Wall of China from space," Wilner said. The boon in political advertising won't spread evenly across the nation as only primary and battleground states will get the most solicitations for ads, she added.

In anticipation of the advertising boon, two key stations in Iowa and New Hampshire reportedly rejected requests by Republican candidate Sen. Marco Rubio (R-Fla.) to reserve ads beginning in December, The National Journal reported in June. The stations, political analysts said, appeared to be trying to withhold reservations so that candidates would compete for those slots closer to the primaries, thereby driving prices higher.