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Nearly six in 10 Americans support a path to citizenship for illegal immigrants, but with Republicans firm in their opposition by a wide margin - a challenge for a party torn between reflecting the views of its base and seeking to broaden its appeal.

With negotiations in Washington proceeding, 57 percent in the latest ABC News/Washington Post poll support the most contentious part of immigration reform, a process by which illegal immigrants may gain citizenship. Two other elements - stricter border control and more visas for highly skilled workers - win broader backing, from 80 and 72 percent, respectively.

See PDF with full results, charts and tables here.

Partisan and ideological divisions on a path to citizenship remain vast and essentially unchanged in recent months. Democrats support the idea by a wide 73-25 percent; independents by a majority 58-39 percent. Republicans oppose it, 60-35 percent - numerically a new low in support in three ABC/Post polls since last November, albeit just by 2 percentage points.

Similarly, 78 percent of liberals and 59 percent of moderates favor a citizenship process; that falls to 42 percent of conservatives, including 37 percent of "very" conservatives.

Tellingly, a path to citizenship is backed by 69 percent of nonwhites, including 80 percent of Hispanics and 67 percent of blacks - groups that overwhelmingly favored Barack Obama in his successful re-election campaign. That falls to 51 percent of whites, who preferred Republican Mitt Romney by 20 points.

There's also a sharp generational break in this poll produced for ABC by Langer Research Associates: Adults younger than age 40 - a group that decisively favored Obama over Romney in the election - back a path to citizenship by 67-30 percent. Support drops to a bare majority, 51 percent, among those 40 and up, a majority of whom voted for Romney .

Those differences underscore the challenges facing Republican Party leaders: Stay loyal to the policy preference of their party faithful and core support groups including whites, older adults and conservatives, at the risk of clinging to an inadequate support base; or seek to appeal to groups such as Hispanics, younger adults and moderates, at the risk of alienating the party's core.

BORDERS and VISAS - Two other issues in the debate, as noted, are far less divisive. Substantial majorities overall and across groups support stricter border control and a more lenient visa program for skilled workers alike.

Views on skilled workers, notably, show no partisan divisions at all. Support for an expanded program for skilled workers declines among blacks, to 56 percent. It's supported by larger majorities in basic demographic and political groups ranging from a low of 65 percent (of Midwesterners) to a high of 90 percent (among Hispanics).

Hispanics are at the other end of the spectrum on increased border security; 61 percent support it, a low among groups, compared with 93 percent among Republicans.

Overall views on a path to citizenship and border security are essentially unchanged compared with ABC/Post polls earlier this year and in late 2012, but far higher than they were in a differently phrased question in an ABC/Post poll in 1984. (The question on visas - specifically, allowing more highly skilled individuals from other countries to live and work in the United States - is a new one.)

Bipartisan groups in the Senate and House are expected to unveil their proposals for an immigration reform bill shortly, building on an agreement between labor and business representatives on the contours of a new "guest worker" visa program. The legislation is expected to include a path to citizenship, stricter border security and more visas for high- and low-skilled workers alike.

Work on the issue in Congress already has paid one dividend: An ABC/Post poll last week found favorable views of the Congress jumping to 56 percent among Hispanics, up by 21 points from November 2011 and the only group in which it reaches majority popularity. Again the risks, particularly to the GOP, are of backlash from its base if immigration reform goes forward - and backlash from others if it doesn't.

METHODOLOGY - This ABC News/Washington Post poll was conducted by landline and cell phone March 27-30, 2013, in English and Spanish, among a random national sample of 1,014 adults. Results have a margin of sampling error of 3.5 points. The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by SSRS/Social Science Research Solutions of Media, Pa.