By Ginger Gibson and Grant Smith
DES MOINES, Iowa (Reuters) - In 2015, it wasn't the new breed of political groups that can raise as much as billionaires will give them that spent the most on the U.S. presidential race.
Rather, it was candidates' campaign organizations, with strict fundraising caps, that led the way, Federal Election Commission filings released on Sunday showed.
Official campaigns, which can accept donations of only up to $2,700 from individuals for the primary races, spent $322 million in 2015, the filings showed.
By contrast, Super PACs, which came into being after a controversial Supreme Court ruling in 2010 and can raise and spend unlimited amounts, spent under $200 million on the effort to elect the next president.
Super PACs usually spend heavily on political advertising, but are barred from sharing strategy plans or even schedules with the candidates they support.
Much of the money raised by official campaigns has to fund travel and accommodation costs, but they also spent heavily on advertising in 2015, perhaps in part because they are generally entitled to much cheaper television rates.
Among the presidential candidates, U.S. Senator Bernie Sanders, a Democrat from Vermont, spent at least $10 million on advertising in the last three months of the year. His rival, former secretary of state Hillary Clinton, spent at least $8 million.
On the Republican side, U.S. Senator Marco Rubio spent the most on television ads, at $8 million, followed by retired neurosurgeon Ben Carson at $3 million.
Even when it comes to fundraising, campaigns are leading the way, bringing in $449 million in 2015 against $341 million for the Super PACs.
Whether this pattern will hold in 2016 is unclear. Super PACs had $158 million in hand to spend in the coming months, while the campaigns collectively had $128 million.
(Editing by Kevin Liffey)