Sen. Susan Collins is engaged to be married to Thomas A. Daffron, a longtime Senate senior staff member and a consultant.

A small, private ceremony is expected to take place in Maine this summer at a date still to be determined.

“What matters the most to me is to have my family there and Tom’s family there,” Collins told the Bangor Daily News on Thursday night before heading to Munich for a security conference. “So we’re debating whether we should have it in my hometown of Caribou or Bangor, where I live now … I’m sure it will be a very happy occasion with a lot of joy.”

The two met when they both worked for Sen. Bill Cohen in the late 1970s, but it wasn’t until a few years ago that they developed a personal relationship.

Collins was elected to the U.S. Senate in 1996 after serving as founding executive director of the Center for Family Business at Husson College in Bangor. She previously served in the cabinet of Maine Gov. John McKernan as commissioner of professional and financial regulation and as New England administrator of the U.S. Small Business Administration.

Daffron, 73, is the chief operating officer of Jefferson Consulting Group, a Washington, D.C.-based consulting firm, where he oversees day-to-day operations. Before joining the consulting group, Daffron held a variety of senior management positions in government and the private sector.

Originally from New York City, Daffron has served as chief of staff to former Sens. Bill Cohen of Maine and Fred Thompson of Tennessee. He also served as chief of staff to Lisa Murkowski of Alaska and was the national campaign manager for the presidential campaign of Elizabeth Dole.

He also consulted for Collins on all three of her campaigns for U.S. Senate.

Earlier in his career, he worked as a newspaper reporter, editorial writer and public relations executive. He also held the position of senior vice president and chief operating officer for the Baltimore Orioles.

“He’s extraordinarily smart, has a wonderful sense of humor and is a great friend,” Collins said. “Those qualities matter a lot to me.”

While their personal relationship has been kept relatively quiet, the couple recently purchased a four-bedroom townhouse together near Collins’ Capitol Hill office. It serves as Collins’ home away from home when she’s not in Bangor. Daffron uses the basement apartment of the house, said Collins. He also owns a house in Maryland.

“We both really enjoy swimming and kayaking and being at the lake, that’s something we definitely have in common,” Collins said. “We’re both avid readers and care a lot about politics and public service as well. I think we have a great deal in common.”

Collins, 59, was born in Caribou, where both of her parents, Donald and Patricia, each served as mayor. Her father served in both houses of the Maine Legislature. Today, her brothers Sam and Gregg operate a fifth-generation lumber business, S.W. Collins Co., founded by their family in 1844.

During Collins’ time in office, she has led the Homeland Security and Governmental Affairs Committee, helping to rewrite much of the way the nation’s security agencies operate and share information after the Sept. 11 attacks. She also serves on the Senate Appropriations and Armed Services committees, as well as the Special Committee on Aging.

“You know, one of the difficult parts of my life is that I have to plan even the most important events of my life around the Senate schedule,” Collins said. “So that’s one reason we haven’t set an exact date for the summer, yet. I’m trying to figure out the recess schedule, and when we could get married and go on a honeymoon. It’s not easy to figure out. But it’s obviously very important. I hope people will understand if I take a little time off.”