It’s no wonder it took so long. The bipartisan immigration bill introduced this week in the Senate is a hefty, voluminous achievement.

It’s 900 pages of complex political calibrations will need a strong binding to withstand the onslaught to come.

The bill lays out a rough, but realistic, road to citizenship for the approximately 11 million undocumented immigrants in the United States.

They will have to pay a series of phased-in fines adding up to $2,000, demonstrate a knowledge of civics and English and meet other requirements before obtaining Lawful Permanent Resident Status after 10 years. Citizenship then will be three more years away.

The good news, however, is that if the law is enacted, these immigrants soon would be able to obtain a provisional status allowing them to work legally in the U.S. while they begin their long wait.

Meanwhile, the bill promises to eliminate the lengthy backlog of immigrants awaiting entry on employment or family-based visas.

The anti-reform caucus, in which Republican politicians from Texas, one of the nation’s most Hispanic states, play an especially robust role, already is labeling the proposal “amnesty.”

This is something of a head-scratcher: It’s hard to recognize the legislation’s arduous, 13-year path to citizenship as anything other than a gauntlet. Fortunately, young immigrants who were brought to the U.S. as children would be eligible for citizenship after five years.

Like much of the bill, the long wait for citizenship was a necessary compromise forged by the bipartisan “Gang of Eight” senators.

The legislation is a delicate balance of trade-offs, supplying more visas for high-skill workers and restricting visas based on family relationships. It promises to reduce the backlog of visa seekers in general while eliminating “diversity visas,” which help seekers from nations that typically haven’t produced large numbers of immigrants to the U.S. It mandates investment in border security to keep unskilled immigrants out, and a new “W-Visa” program designed specifically to welcome them in.

The legislation lives up to its billing as “comprehensive.” It would reach into every corner of U.S. immigration policy, including a requirement that employers use the E-Verify system to check the status of prospective employees and the creation of a “biometric green card” for authorized noncitizen workers.

It also contains initiatives we aren’t entirely sure about. Of particular concern are the proposed border security benchmarks, which have to be met before undocumented immigrants already in the U.S. can advance on the path to legal status and citizenship.

The benchmarks, including specific “effectiveness” metrics for rebuffing attempted border entries, make sense as security goals. The aspirations of an undocumented immigrant in, say, Atlanta, however, shouldn’t be tied to benchmarks 1,500 miles away — and utterly outside her control — along the Mexican border.

The comprehensive, balanced and, yes, compromised nature of the bill is both its chief strength and its greatest vulnerability. Opposition to immigration reform is real. Although Republican leaders appear to understand that reform is in their political interest, more Republican voters oppose a path to citizenship than support it. (A majority of Democrats and independents, by contrast, support it.)

To keep the bill on track will require fortitude from Sen. Marco Rubio, the Florida Republican who has linked his political fortunes to immigration reform. Rubio courageously has appeared on conservative radio shows to dispel myths and fears about immigration. He must do more of that in the weeks ahead.

To be successful, Rubio also will need the tacit approval of Senate Republican leader Mitch McConnell and House Speaker John Boehner, who will have to engineer a winning vote in both houses of Congress with less than full support from Republican members.

Immigration reform promises to be a messy process, and not everything will go according to plan. The legislation introduced this week, however, moves the nation in the right direction. It deserves support.

Editorial by Bloomberg View