WASHINGTON » The two women might at first seem more like political rivals than a reminder of the way things used to work in Washington.

Esther Olavarria, a Democrat, left Cuba as a child, worked as Sen. Edward M. Kennedy’s top immigration lawyer and now holds a post in the White House. Rebecca Tallent, a Republican, left suburban Arizona and became Sen. John McCain’s chief of staff, briefly advised Sarah Palin in 2008 and is now a top policy aide to Speaker John A. Boehner of Ohio.

But if there is any way to unlock the immigration stalemate in Washington, colleagues say these two might find it.

A decade ago, the two women spent months in marathon backroom deal-making sessions as they repeatedly tried to bring lawmakers together on overhauls that would have given legal status to immigrants, secured the border and opened the country to more legal workers. In the process, they formed a friendship that transcended party affiliation.

"What they have is superior knowledge of the subject that exceeds any other staffers and any members," said Mark Salter, a veteran of immigration battles who served as a top policy adviser and chief of staff to McCain. "That gives them an advantage."

Or as one longtime immigration lobbyist put it: "We hear from everybody that Boehner wants to get to yes but he doesn’t know how. So he hired Becky to find out."

Tallent, 34, is a key player in writing what Boehner and other House Republicans call guiding principles for an immigration overhaul. The goals, which are expected to be outlined in detail in the next week, are likely to include bolstered border security and enforcement inside the country, fast-track legalization for agricultural laborers, more visas for high-tech workers, and an opportunity for young immigrants who came to the country illegally as children to become U.S. citizens.

At the White House, Olavarria, 56, is charged with finding a compromise that Democrats and activists can live with. Both sides say they expect the two women to immerse themselves in back-channel talks, if they have not already.

Tallent and Olavarria declined to be interviewed for this article.

The two began working together on immigration in 2003, in the backrooms of Capitol Hill. Olavarria was the top immigration adviser to Kennedy, and Tallent held a similar position under Republican lawmakers, including McCain. The two senators had forged a bipartisan approach to immigration, and the women took their cues from what they had seen: an eagerness to fully engage — something missing from President Barack Obama’s relationship with Boehner.

"They understand how this works," said Angela Kelley, a longtime immigration activist who has known both women for years. "They never deviated from standing by their boss. But they always treated each other with a lot of respect, and they never got to this point of personal breakdown where they couldn’t come back from it."

Today, the immigration landscape the women face is potentially more favorable. Obama is under intense pressure from Latinos who supported his candidacy to end mass deportations and offer a path to legal status to the estimated 11 million illegal immigrants in the country. Many Republicans believe that if Boehner can find a way to overhaul the system, he may be the party’s best hope of repairing a deep breach with Hispanic voters in presidential elections.

Others are highly skeptical about how much the two women can accomplish. Michael Torra, who worked as a legislative aide in the House with Olavarria and Tallent in 2003, said that their history of working together may not be enough to overcome opposition to a deal by Tea Party Republicans and immigration opponents.

"Obviously, you need more than excellent staffers," Torra said. "You need the political will from the people they work for."

Friends of both women say they have different styles but similar ambition and experience. Olavarria, known on Capitol Hill for holding an annual July 4 pig roast, is soft-spoken and even-keeled, while Tallent, a generation younger, is more animated. Ana Navarro, a Republican strategist who has worked with both, called them "hard-charging, low-profile, serious women."

Olavarria was raised in Miami, graduated from the University of Florida law school and spent the first part of her legal career representing Haitians and other immigrants. She later moved to Washington as an eager legal advocate, full of hope and energy.

"I came here to change the 1996 immigration laws, and nothing has happened yet," she said in 2005 as she and Tallent and other congressional staff members were taking a break from negotiations. The scene was captured in a series of documentary films called "How Democracy Works Now."

Sitting in a conference room that day in Kennedy’s warren of offices, Tallent laughed at how she had originally been interested in environmental issues, but stumbled into the immigration fight.

The daughter of an Air Force pilot, Tallent was born in Del Rio, Texas, less than 10 miles from the border that would define much of her career. She was raised in Tucson, Ariz., and earned a political science degree from Carleton College in Minnesota before moving to Washington for McCain. She has also worked for Rep. Jim Kolbe, another Arizona Republican, who fought unsuccessfully for an immigration overhaul.

"My plan, actually, was to be out here for one year to answer some phones and then go back to Arizona," Tallent said in the documentary. "It’s four years now."

For several intense months that year, she and Olavarria haggled over minute legislative details as the politicians grappled for support from business, labor and immigrant leaders. Deals were made and then crumbled as critics pounced from all directions. Olavarria was responsible for soothing the unions, while Tallent wooed the business community.

The effort culminated that spring when Kennedy, McCain and a handful of House members announced landmark legislation to grant legal status to millions of immigrants, secure the border and increase the flow of legal workers. Happy but exhausted, Tallent and Olavarria and their colleagues savored the victory.

"At some point next week, we should all get together and have a little celebration," Tallent said to Olavarria and others.

The festive atmosphere did not last long. The legislation they helped write in 2005 died amid partisan bickering in Congress the following year, as did similar efforts to reach a deal in 2007.

Late last year, Olavarria and Tallent took a bipartisan trip to the New York Film Festival, where they joined about a half-dozen other congressional staff members and advocates in a small theater at Lincoln Center and watched themselves in the immigration documentary.

"We were calling it old home week," said Margaret Klessig Edmunds, who was chief of staff for Rep. Jeff Flake, R-Ariz., in 2005.

Afterward, Tallent and Olavarria joined some of the others for drinks at a restaurant across from the theater. Edmunds said there was some ribbing between the two women, who asked each other, she said, "Aren’t you sorry you didn’t take that deal back then?"

© 2014 The New York Times Company