Here’s the good news for station owners and networks in an analysis of this year’s political media spending out today from ad forecasting firm Borrell Associates: Cash will continue to flood most markets, with broadcasters seeing $4.6B, an 11.5% increase over 2010, the previous midterm election year. The problem? Broadcast TV’s take represents 55.4% of the $8.3B to be spent for ads in all races and ballot issues — down from its 57.5% share of the $7.2B spent in 2010. Cable and online are “the only media choices projected to gain share” this year, the report says. Cable, with $719.3M, will account for 8.7%, up from 6.9% four years ago. And online’s $271.2M is up 1,825.2% vs its $14.1M in 2010. Although online will just account for three cents of every ad dollar spent on all of this year’s contests, “current forecasts call for explosive growth to continue, nearing the billion-dollar level by 2016’s Presidential election.”

Display and video will account for three quarters of this year’s online spending. Politicos are “fascinated” by their ability to use display ads to “direct messages to specific groups of voters quickly and (relatively) cheaply, without buying expensive lists or depending upon corps of volunteers to stuff envelopes.” Meanwhile, millennial voters “are much more likely to turn to streaming video and social media” than others are for political info.

Broadcasters’ share of political spending will shrink again in 2016, to 52.6%, yet few likely will worry considering how big pie will grow for the presidential election year without an incumbent. Borrell expects spending to hit $12.3B with cable accounting for 10%, and online up to 7.7% — ahead of newspapers, which will have 7.1%. But the trends are clear: “It is no longer a question whether other media choices will eventually surpass broadcast TV for political ad share, it is only a question of when the event will occur.”