New York Mayor Michael Bloomberg and philanthropists Bill and Melinda Gates top the donor list to proponents of Amendment 66, the school finance measure that includes a $950 million tax hike.

Bloomberg Philanthropies added $1.05 million to the effort, and the Gateses contributed $1 million, pushing the Yes on 66 fundraising total past $10.2 million.

Those two contributions accounted for the vast majority of the $2.54 million raised in the last two-week reporting period for Colorado Commits to Kids, the issue committee behind the measure.

Bloomberg’s involvement in Colorado issues already has proved a political lightning rod.

Colorado Republicans have blistered Bloomberg ever since Democrats unveiled their package of gun-control legislation in February. They called Bloomberg, who founded Mayors Against Illegal Guns, the “de facto governor of Colorado” and argued he was calling the shots in the gun debate.

Senate Republicans even displayed a New York flag in their office, complete with pictures of Bloomberg and Gov. John Hickenlooper.

The New York mayor also became involved in the recent legislative recall elections. Bloomberg donated $350,000 to opponents of the September recalls of state Sens. John Morse and Angela Giron, who had supported the recently passed gun control legislation.

Proponents of Amendment 66, including Hickenlooper, said they welcomed the support of someone who has been an advocate for education reform. Amendment 66 would put more money toward full-day kindergarten, at-risk students and English language learners, and charter schools plus help fund reforms already implemented by previous legislation.

“We think the mayor has a long history of supporting education reforms, and we’re happy to have him supporting the education reforms Amendment 66 would bring,” said Yes on 66 spokesman Curtis Hubbard. “We’re focused exclusively on education and delivering a national model for public education to Colorado. And the mayor recognized Amendment 66’s promise for public education.”

In a statement released through the campaign, Bloomberg called the measure “a rare, comprehensive blend of smart investments with smart reform that will brighten the state’s educational and economic future.”

But opponents pounced on the Bloomberg donation.

Kelly Maher, executive director of Amendment 66 opponent Compass Colorado, slammed Hickenlooper for criticizing out-of-state money entering the gun debate in a recent USA Today story while welcoming the donation toward school finance and the tax hike.

“Gov. Hickenlooper’s hypocritical comments are just yet another example of his inability to take a firm stand on any issue,” Maher said. “One minute he is against out-of-state political money, but if it’s for his billion-dollar tax hike, baby, then it’s praiseworthy.”

Supporters of the measure have spent millions already on television advertising and unspecified campaign work. Opponents have had a much more limited presence on TV.

Opposition group Coloradans for Real Education Reform had not filed their campaign finance report by late afternoon Monday.

Another opposition group, Kids Before Unions, reported $4,325 in donations for this period, led by $1,200 from the Colorado Union of Taxpayers. That pushed its total contributions to $11,640.

Mail-in ballots already have been distributed for the Nov. 5 election.

Kevin Simpson: 303-954-1739, ksimpson@denverpost.com or twitter.com/ksimpsondp

Lynn Bartels and Kurtis Lee contributed to this report.