A bipartisan group of eight senators drafted the bill and then shepherded it through the Senate Judiciary Committee. The measure is supported by the White House, the AFL-CIO trade union federation and the Chamber of Commerce, the pro-business lobbying group. Many Republican political strategists view immigration reform as vital to the party's efforts to show a more welcoming face to the rapidly growing bloc of Hispanic voters.
Despite the widespread support, the bill's passage is by no means assured, given that 60 votes are usually required to overcome procedural road blocks to end Senate debate and pass legislation. There are currently 54 senators, including two independents, in the Democratic caucus, and 45 Republicans.
That has put Sen. Mario Rubio, a Cuban-American, in an awkward position. The Florida Republican helped negotiate the bipartisan bill now headed to the full Senate, and recently has called for changes as he tries to keep faith with tea party supporters and other conservatives who will vote in the 2016 presidential primaries and caucuses.
Internal divisions in the Republican Party, deeply held differences over policy, concerns over costs and more add to the complexity of legislation that Senate Majority Leader Harry Reid has said must come to a final vote by July 4.
The memo also advises supporters to emphasize that 100 per cent of the US-Mexican border will be put under surveillance, that immigrants who gain legal status won't be eligible for welfare "for over a decade" and that anyone entering the United States unlawfully in the future will be barred from legal status.
