The advice from veterans was curt: enjoy the euphoria of the moment, because it won’t last.

The House of Commons has stood at the center of Britain’s political crisis during the last two years, as the government struggled to get its Brexit plan through Parliament while lacking a majority.

Every vote counted and every lawmaker mattered. But with Mr. Johnson’s big new majority things have fundamentally changed. The days when the niche Parliament TV channel could draw more than a million viewers to the drama of knife-edge Brexit votes are over.

New lawmakers are likely to find themselves either part of an impotent opposition or lobby fodder for a government with so many bodies that individuals simply don’t matter.

“Winning a seat for the first time is one of the great moments in life, for most people it is the end of a long cherished ambition,” said Tim Yeo, a former Conservative lawmaker who arrived in Parliament in 1983, after Margaret Thatcher won an equally huge victory. But, if you are part of a very large new intake, what awaits you is a “rude shock,” he said.

“You arrive at Westminster and you are the new boy or girl at what turns out to be a rather bigger school than you thought,” he said. “You suddenly realize that you are a person of the utmost insignificance.”