Frustrated by being left out of an immigration overhaul, gay rights groups are pushing to adjust a bipartisan Senate bill to include gay couples. But Democrats are treading carefully, wary of adding another divisive issue that could cost Republican support and jeopardize the entire bill. Both parties want the bill to succeed. But agreeing on the basic framework for the immigration overhaul, which would create a long and costly path to citizenship for the estimated 11 million people in the U.S. illegally, was no small feat. And getting it through a divided Congress is far from a done deal. Even so, gay rights groups, their lobbyists and grassroots supporters are insisting the deal shouldn’t exclude binational, same-sex couples — about 28,500 of them, according to a 2011 study from the Williams Institute at the University of California School of Law.