WASHINGTON - Outside groups set up to benefit specific candidates have raised twice as much as the candidates themselves so far in the 2016 presidential race — and groups reported to have close ties to a candidate account for 96 percent of total outside fundraising, according to a new report from the Brennan Center for Justice at NYU School of Law.

Of the $283 million raised by outside groups in 2015, $273 million was raised by what the study calls “shadow campaigns” — groups that have reported ties with the candidates they support. These ties include the candidate fundraising for the group and candidates’ former high-level staff working for the group, among others.

This connection to the candidates is crucial to the fundraising success of the highest-performing outside groups. All 10 of the groups that raised $10 million or more reportedly have connections to their favored candidate, according to the study.

In the past, groups and candidates were more reluctant to explicitly tie themselves together. But this cycle, shadow campaigns seem more brazen than ever about telegraphing their connections to candidates — and big donors are rewarding those groups that have close ties.

“In Citizens United, the Supreme Court argued we don’t need to worry about outside spending because it’s independent — it can’t corrupt candidates because they don’t control it,” said Ian Vandewalker, author of the report and counsel in the Brennan Center’s Democracy Program. “But the biggest money in this election is going to the outside groups that seem to be the least independent, by any common-sense understanding of that word. When candidates fundraise for outside groups, give up former staff to run those groups, or count the groups’ money in their own fundraising announcements, everyone knows what’s going on.”

The study, Shadow Campaigns: The Shift in Presidential Campaign Funding to Outside Groups, includes a full analysis of candidate and shadow campaign fundraising for all 21 candidates.

More key findings:

• Based on press reports, $213 million was raised by outside groups run by or working with former high-level staff of the candidate, $147 million was raised by groups that the supported candidate raised funds for, and $65 million was raised by groups that received a public signal of approval by the candidate or a campaign spokesperson.

• For a majority of candidates, shadow campaigns have raised more than their favored candidates’ campaign committees. Brennan Center data shows shadow campaign fundraising accounts for at least two-thirds of the fundraising in support of 12 of 21 candidates.

• The candidate who benefited the most from this trend is former Florida Gov. Jeb Bush. Shadow campaign groups supporting Bush and benefiting from his fundraising efforts took in $108.5 million, a record-breaking amount that is almost 10 times the $11.4 million raised by his campaign.

• Republican shadow campaigns have outraised their Democratic counterparts by a factor of 12. Much of the difference is driven by the top fundraiser in each party. Outside group fundraising in Jeb Bush’s favor was significantly higher than the total raised by his campaign. Whereas Hillary Clinton raised the most of any candidate from either party ($47.5 million), and shadow campaign groups in her corner collected a substantial amount ($20.3 million), outside money was still less than half the direct contributions to her campaign.

• This presidential election has already seen unprecedented levels of money raised by outside groups supporting a specific candidate. At this point in the 2012 cycle, the pro-Romney Restore Our Future had raised $12 million, and the pro-Obama Priorities USA Action had raised $3 million. By comparison, at the same time in this election cycle eight candidates each stand to benefit from shadow campaigns with more than $10 million raised.

• Although campaigns are subject to strict contribution limits, $270 million, or 95 percent of the outside money, was collected by groups subject to no limits whatsoever.

• Despite the massive sums reported here, our analysis underestimates outside fundraising because “dark money” organizations have not yet been required to report their revenue.