Sen. Jeff Flake, R-Ariz., has had quite a week.

It began with his 50th birthday, which officially happened 15 minutes before midnight on New Year’s Eve, and ended with his being sworn in as the new junior senator from Arizona.

“It was just phenomenal,” Flake tells HOH. “It was really neat.” He sounded overwhelmed, happy and joyful just moments after his swearing-in.

For the father of five, the highlight of the week, however, was the engagement of his daughter Alexis, 21, to Jason Arias, 26, on the Capitol Dome on Wednesday.

“Our daughter Alexis is a senior at Brigham Young University,” Flake says. Alexis is getting her degree in broadcast journalism, so she spent the summer of 2012 in D.C. as an intern for ABC’s “Good Morning America.” Arias, another BYU student, was also interning at a public affairs firm in the District when they met.

“Their first date was at the Congressional Baseball Game,” the senator says, referring to the longtime CQ Roll Call tradition. Flake plays on the GOP team. “Cheryl and I were both at their first date,” he says, referring to his wife.

Alexis and Jason have been together ever since.

According to the senator, Arias surprised Alexis twice Wednesday. He flew into D.C. without her knowing. While she was taking a tour of the National Archives, one of the archivists told her that there was a special exhibit behind a closed door. The door opened and there was Arias.

Two hours later, Flake continues, the family had a tour of the Capitol Dome.

At the top, the young couple hung back from the group. Arias got down on one knee and Alexis said, “Yes.”

“They will both graduate in April,” Flake tells HOH, “and will probably get married in May.”

The couple will settle in the Washington area next summer.

Correction: 8:33 a.m., Jan. 4

An earlier version of this post misspelled the name of Jason Arias.