• by David Goetzl  @dgoetzl, July 5, 2007

If political advertising dollars take up a large portion of cable news networks' inventory, advertisers may be prompted to spend more with news networks in the ongoing upfront to lock in rates.

According to Nielsen, current political ad spending marks an early start for a presidential campaign, though not as early as the 2000 race, when candidate George W. Bush started advertising more than two years before Election Day.

Six presidential hopefuls have already aired TV spots, providing a boon for local stations well before the expected high tide next year -- and Democrat Hillary Clinton has yet to hit the airwaves.

Republican candidate Mitt Romney leads the pack with 4,252 local spots through June 10, more than double all the other candidates combined, according to new data released by Nielsen.

While neither Clinton nor Republican Rudy Giuliani have launched TV offensives yet, top Democratic contender Barack Obama, who just raised a reported $31 million over the last three months, started advertising June 27 (in Iowa). That means stations could find millions more heading their way soon.

In the last few weeks, Democrat Chris Dodd has been in heavy rotation, running more than 1,660 spots. Dodd has run the third-most spots behind Romney and Democrat Bill Richardson's 2,232 (all in Iowa and New Hampshire).

Two other candidates, John Edwards (D) and Duncan Hunter (R), have run a handful of spots. Romney's 4,252 local spots have aired in seven markets, notably and not surprisingly New Hampshire and Iowa, sites of the first primary and caucus, respectively. But he's also aired more than 300 spots each in South Carolina and Florida.

Romney and Dodd are the only candidates to use national cable, running 297 and 4 spots, respectively.

Despite passing on TV so far, Romney competitor Republican Rudy Giuliani has used a heavy rotation of radio spots (642), well above Romney's use of the medium (378) -- they are the only candidates to use local radio so far.