WASHINGTON — Rep. Peter Welch’s sister, Maureen, had better intelligence than the five-term Vermont congressman about Pope Francis’ upcoming trip to the United States and his historic address to Congress.

“She called before the announcement and said, ‘The pope is coming, can I have your ticket?’” recalled the Democratic lawmaker.

He eagerly said yes to Maureen — Sister Maureen, an Ursuline nun who has been a member of the order for 50 years.

While Welch’s decision was somewhat easy, other lawmakers are struggling with an extraordinary demand — from spouses, family, friends, constituents — for the one ticket they get for guests to sit in the upper galleries of the House chamber when the pontiff addresses Congress on Sept. 24. A chance to see and hear the 78-year-old Argentinian famed for making the comfortable uncomfortable is the hottest ticket in Washington.

“We have more requests for this appearance than anything anybody can ever recall around here,” Senate Majority Leader Mitch McConnell, R-Ky., said weeks ahead of the event.

The first time a pontiff will be addressing Congress rivals a presidential inauguration and State of the Union wrapped into one.

The president’s Cabinet, the diplomatic corps and members of the Supreme Court, six of whom are Catholic, are expected to join senators and House members in the seats on the floor of the chamber. The House recently took the unusual step of voting to limit the people who can sit in those prime seats, essentially barring former members.