The coalition of business and progressive groups that back the Senate’s far-reaching immigration bill gave politicians far more in donations than rival advocates for reduced immigration, according to a new report by MapLight, a group that tracks money in politics.

Legislators received donations worth $63.2 million from business and progressive groups in favor of an immigration rewrite, but only $2.6 million from opponents of the “Gang of Eight” bill that passed the Senate by a 68-32 vote Thursday. The GOP-led House of Representatives is expected to take up a separate bill after the July 4 recess.

That 24 to 1 ratio doesn’t include the factions’ spending on lobbyists, advocates, pollsters, public relations agents, or TV advertising.

It also doesn’t count the value of favorable media provided by friendly journalists, or the friendly relationships established between politicians and familiar lobbyists, many of whom are former employees of the senators.

Similarly, the MapLight count doesn’t include the value of future campaign-trail aid that companies, foundations and especially unions can offer legislators to win their votes.

The cost of those promises and advocacy efforts may far exceed the visible, short-term donations. For example, the U.S. Chamber of Commerce is reportedly spending more than $10 million running TV ads that portray the immigration bill as a border security measure.

One study said the pro-bill coalition has spent $1.5 billion since 2007 trying to win an amnesty for 11 million illegals, increase immigration, and boost the inflow of low-wage guest-workers sought by companies.

More donations went to senators who backed the far-reaching bill Thursday.

Backers of increased immigration gave a stream of donations worth $655,252 on average to the 68 senators who voted for the bill and $581,315 on average to the 32 who voted against it.

One standout was Utah Republican Sen. Orrin Hatch, who allied with industry groups to roll back worker-protection measures in the bill. He got $1.14 million from the bill’s backers.

More importantly, Republican leader Mitch McConnell got $1.8 million from the bill’s backers. McConnell ended up voting against the bill, but he didn’t use his position as Senate minority leader to try to rally GOP senators to vote against it.

The Senate’s majority leader, Democratic Sen. Harry Reid, got $1.93 million from the bill’s backers. He pushed hard to pass the bill as quickly as possible, amid growing public opposition.

But donations aren’t the only factors that shape senators’ votes. A politician’s long-standing preferences invites donations from similar-minded groups, including CEOs and foundation directors. Companies often donate to legislators to stay on their good side, regardless of the politicians’ position on many issues.

Politicians need votes on election day, and so they tend to follow the polls rather than the cash.

But the Democratic senators are under intense pressure from their Senate peers and from their leaders to back the bill — despite its impact on low-wage Americans — because it will provide Democrats with a huge wave of voters during the next two decades. The Congressional Budget Office estimates the bill would increase immigration by 10 million people between now and 2023 and 16 million more people between 2023 and 2033, while legalizing about eight million immigrants who are in the United States illegally. If current patterns hold, these immigrants will be overwhelmingly Democratic-leaning.

The GOP caucus voted 2 to 1 against the bill, even though they got a total of $27 million in donations from the bill’s backers, and only $359,945 from the bill’s opponents.

Follow Neil on Twitter