When all is said and done, and all the money contributed to the presidential campaigns is tallied up, more than $2 billion will have been raised and spent on the bid for the White House.

That total, which is roughly the equivalent of Greenland's GDP, will represent the highest amount of money gathered during a presidential campaign. 

According to reports, U.S. President Barack Obama has raised a little over $1 billion with Republican presidential challenger Mitt Romney not far behind. Just for the first 15 days of October, the Obama team pulled in $88.8 million compared with $111.8 million for Romney. While Obama has an advantage with direct contributions, Romney has a huge lead in SuperPAC money.

And in terms of money actually spent so far, the Center for Responsive Politics, a non-partisan organization that crunches campaign numbers, said Obama's campaign has doled out $912 million, while Romney has spent $937 million.

U.S. election rules allow individual donors to give a total of $2,500 to a candidate in the general elections. But there is no limit to SuperPAC contributions. And the influx of outside money has sparked some concerns and criticisms.

Donor secrecy

"In the presidential race the outside groups are generating a lot of heat but not necessarily a lot of light," Sheila Krumholz, executive director of the CRP, told CBC News. "There are hundreds of millions of dollars being raised and spent, much of it in secret, and so that adds to a greater degree of uncertainty."

Both candidates have been able to raise such large sums because both declined the public financing system —  roughly $100 million in taxpayer money — that would have limited  how much they could spend.

"That has been another element to the feeding frenzy here, that they cannot stop fundraising even when it may come at a cost to reaching out to voters they may need to connect with," Krumholz said. "The nominees would have been able to focus on getting out the vote and connecting with voters. Now they're dividing their attention between the voters and the cash constituents."

The Supreme Court's controversial 2010 Citizens United vs. the Federal Election Commission decision gave birth to the SuperPACs, which can raise and spend unlimited amounts of cash. The only restriction is the groups cannot co-ordinate their actions with the candidate they hope to help.

"Every national election in this country sets a record [for spending], but this one will far exceed anything that has happened in the past,"  said Fred Wertheimer, founder and president of Democracy 21, an advocate of campaign finance reform. "The major reason is the misguided Supreme Court decision in the Citizens United case that has changed the landscape of American politics and has wreaked havoc in the 2012 elections."

"The problem here is the money going to outside groups is coming in the form of unlimited contributions, secret money and corporate funds which is the same kind of money that was at the heart of the Watergate scandals," he told CBC News. "So what you have here is massive amounts of potentially corrupting influence money, funding these outside expenditures." 

Record advertising

More money has meant more advertising. According to the Wesleyan Media Project, which tracks advertising in federal elections, more than 915,000 presidential ads have been aired on broadcast and national cable television since June 1 — a 44.5 per cent increase over the last election, which saw 637,000 ads aired.

Obama’s campaign has spent over $238.9 million for 460,000 ads. In comparison, Romney's campaign has only doled out $92.3 million for 170,000 ads. But pro-Romney SuperPACs Crossroads GPS and American Crossroads alone have combined to spend nearly the same as the Romney campaign on ads. Meanwhile, Restore Our Future, another pro-Romney SuperPAC, has spent over $42 million since the end of April.

Both parties have ramped up advertising spending in October, with Obama's campaign having aired $65 million for 97,000 ads compared with $30 million for 43,000 ads for Romney. But Romney was aided by American Crossroads, which spent $28 million for over 26,000 ads. 

During the last month, among outside organizations in the first three weeks of October, Democratic-leaning groups are estimated to have spent 438 per cent more on advertising than they did four years ago, and Republican-leaning groups have increased their spending by 954 per cent.

Narrow focus on swing states

"Couple of weeks ago we surpassed the total amount of advertising in 2008, and so I think we'll easily exceed the million ads airing mark before election day is over," said Travis N. Ridout, a professor and one of the directors  of the Wesleyan Media Project.

"They're advertising in fewer media markets, fewer states this year than in 2008. There are just really nine states, and no one outside of those nine states has really seen any advertising at all, and so you are getting these massive barrages of advertising in places like Denver, Colo., Las Vegas, Nev., and Cleveland, Ohio."

The increase in spending is due, in part, to the higher costs of advertising because of increased competition. Also, the Citizens United case has made it easier to get more money into the system than four years ago, Ridout said.

Bradley A. Smith, law professor and chairman and co-founder of the Center for Competitive Politics, rejected Wertheimer's argument that the money will have a corrupting influence on politicians, saying there's little evidence to support it.

He added that he has no problem with the amount of money being spent on these campaigns.

"It's not very much compared to many things," Smith said. "Compare it to what we spend on potato chips and Barbie doll accessories. Proctor and Gamble will spend $2 billion a year on advertising. It costs money to reach people."

With files from The Associated Press