North Carolina, America's $100-million Senate race?

Washington (AFP) - We have a US election winner -- in the money stakes, at least.

The Senate race in North Carolina is on track to be the most expensive congressional contest in US history, likely surpassing a staggering $100 million while featuring two candidates few Americans know much about.

Such is the intensity of the 2014 midterm elections, in which Republicans hope to snatch six Senate seats from Democrats and thus gain control of the chamber, that outside groups are pouring unprecedented and often untraceable millions into political messaging, wall-to-wall advertisements and on-the-ground electioneering aimed at swaying an election.

With two weeks to go before the November 4 vote, North Carolina -- a state President Barack Obama barely won in 2008 and lost in 2012 -- is the spending spree's ground zero, where polls show Senate Democrat Kay Hagan clinging to a razor thin lead against Republican challenger Thom Tillis.

Election funding monitor the Center for Responsive Politics (CRP) said outside spending in the southeastern US state hit $60.5 million by Tuesday, topping the record $52.4 million in outside spending in Virginia's 2012 Senate race.

With the Hagan and Tillis campaigns already spending $13.6 million, and a flurry of ad buys expected in the final two weeks, North Carolina is assured of entering the record books.

"Given that there's more outside spending reporting by the day, it's certainly possible that we're going to crest that $100 million figure," CRP spokeswoman Viveca Novak told AFP.

- Dark money's long shadow -

The Charlotte Observer, citing donors and public records, estimated money spent in the race will top $103 million, including $22 million in "dark money" from groups that are not required by law to disclose their donors.

The non-partisan Sunlight Foundation noted that millions in spending is not even reported to the Federal Election Commission as it falls outside of campaign reporting windows or is spent by non-political groups.

"If the trend holds up -- you always see a flood of late money at the end, and in North Carolina both candidates are within striking distance of a win -- it'll top $100 million," the foundation's editorial director Bill Allison said.

He pointed to private groups like Americans For Prosperity, the right-wing political arm of the billionaire-industrialist Koch brothers which acknowledged it is spending more than $8 million on North Carolina alone as part of a reported $125 million nationwide operation to help conservatives win.

But the biggest outside player so far in North Carolina is Senate Majority PAC, a Democratic group aimed at preserving the party's leadership in the chamber and which has spent $10.1 million in the state, Allison said.

Sunlight reported last week that independent expenditures in the 2014 cycle totaled $452.4 million nationally.

Races seeing near-record outside money include Colorado, where groups have already poured $47.5 million into supporting or opposing Senator Mark Udall and Republican challenger congressman Cory Gardner, and Iowa, where groups have spent $42.5 million.

If spending is adjusted to inflation, The Washington Post ranked Hillary Clinton's 2000 Senate race as the costliest ever, narrowly surpassing $100 million in 2014 dollars.