A successful ballot drive this year to make it more difficult to amend the state constitution brought together one of the most diverse opposition fundraising drives in recent memory.

To call the coalition “odd bedfellows” would be an understatement.

Special interests, advocacy groups and individuals included immigrant-rights groups and those opposed to a path to citizenship, including former U.S. Rep. Tom Tancredo.

NARAL Pro-Choice Colorado was on board with Colorado Right To Life.

The Colorado Fiscal Institute and Bell Policy Center, two left-leaning think tanks, fought the initiative alongside the fiscally conservative libertarian Independence Institute.

And environmental groups offered a surge of support, including Greenpeace, an international environmental group that assisted with anti-hydraulic fracturing initiatives in Colorado. The organization flew a “thermal airship” blimp over Denver and Boulder urging, “Vote no 71 … Don’t let BIG $$$ rig our democracy.”

Those opposed to Amendment 71 argued that only wealthy special interests would be able to make the ballot if the initiative were to pass, as only they would have enough money to pay signature collectors.

In total, the opposition campaign, registered as Colorado League of Responsible Voters, pulled in more than $1.8 million. But it paled in comparison to fundraising by proponents, who reported more than $5.6 million over the course of the election.

Final campaign finance reports for issue committees were filed on Thursday.

Both camps had an impressive fundraising push at the end of the election, with proponents pulling in $898,510, and opponents reporting more than $1 million.

The oil and gas industry led much of the financial support for proponents.

Amendment 71 makes it more difficult to amend the state constitution by requiring signatures from all 35 state Senate districts for a proposal to make the ballot. Of the total required signatures-currently 98,492-the number collected from each district needs to equal at least 2 percent of the registered voters in those districts. If proposals make the ballot, it would take 55 percent of the statewide vote to pass.

Colorado voters backed Amendment 71, known as “Raise the Bar,” with nearly 56 percent support.

The oil and gas industry set its sites on the measure following attempts by environmental groups to place issues on the ballot that would crackdown on hydraulic fracturing, including allowing local governments to ban fracking operations.

If it’s more difficult to amend the state constitution, it’s less likely that those anti-fracking proposals would make the ballot. Environmental groups failed this year to make the ballot under existing parameters.

Protecting Colorado’s Environment, Economy and Energy Independence, an advocacy group for the oil and gas industry, contributed more than $2.8 million to the effort. Vital for Colorado, another group that promotes the benefits of energy production in Colorado, added another $600,000 to the drive. Other oil and gas and business interests also contributed.

Opponents were largely kept afloat by the National Education Association, which contributed more than $1.1 million. Environmental groups, including Conservation Colorado, added $265,000 to the effort. Unions, including United Food and Commercial Workers and AFL-CIO, also assisted with funding the opposition.

All of the groups have an interest in pushing issues by way of the ballot, especially constitutional amendments.

Two separate opposition committees also formed to fight Amendment 71, though they only combined for $1,100.