Pro-government lawmakers accused Mr. Sadat of leaking drafts of the law to foreign embassies, and of faking the signatures of 16 fellow lawmakers on another proposed law that he had drafted. Mr. Sadat denied the accusations, saying he had circulated his criticism only in a news release via email and his website.
Mr. Sadat’s expulsion highlighted the lopsided balance of parliamentary power favoring the president and his security forces, which exert great influence through a deep bench of pliant and conspiracy-minded politicians.
“We saw that Sadat was working against the Parliament and against the state,” said Alaa Abed, a lawmaker who voted against Mr. Sadat. In an interview, Mr. Abed insinuated that Mr. Sadat was in the pay of foreign powers, then abruptly ended the call.
Anwar Sadat, Egypt’s third president, was killed by fundamentalist army officers in 1981. For many years, his soft-spoken nephew was seen as a relatively gentle opposition voice. But in recent years, as Mr. Sisi has become increasingly authoritarian, Mr. Sadat has show more grit, and there has been some speculation of late that he may run in the presidential election planned for near year.
As the expulsion vote proceeded, Mr. Sadat exited the Parliament, telling journalists, “It’s not the end of the world.” He did not offer further comment, but in an interview with The New York Times last week, he said the draft law that targeted aid groups was rooted in a pervasive belief inside Egypt’s ruling class that foreign money had played a role in fomenting the uprising that toppled President Hosni Mubarak in 2011.
“They believe it’s all a big conspiracy,” he said. “But that’s not logical. The truth was that young people were fed up and tired of a regime that had been in power for 30 years. They were full of anger.”
Some critics saw the move against Mr. Sadat as a pretext to neutralize him in the run-up to the 2018 election. Mr. Sisi, who came to power in 2013 after the military ousted his predecessor, Mohamed Morsi of the Muslim Brotherhood, has not yet said whether he will stand for election. But at this point, it is hard to see how an effective opponent could emerge.
Mr. Sisi and his supporters exert a powerful grip on the security forces, politics and the media. Thousands of political rivals are in jail or in exile. In recent months, the government has gone after prominent lawyers and rights activists with prosecutions that have frozen their bank accounts, rescinded their ability to travel abroad and could ultimately imprison them for lengthy terms.
“We are approaching critical times, and the regime needs to eliminate any possible competition,” said Rabab el-Mahdi, a political scientist at the American University in Cairo. “They want to curtail the public sphere, and cracking down on Sadat, one of the few career politicians who posed any threat, is part of that.”
Mr. Sadat is the second person to be expelled from Egypt’s Parliament in the past 12 months. Tawfiq Okasha, a television presenter turned politician, was expelled in March 2016 after he had dinner with Israel’s ambassador to Egypt.
In a phone call Monday evening, an aide to Mr. Sadat declined to speculate on whether Mr. Sadat might run for president, saying it was “too early to consider.”
The one issue on which Mr. Sisi has proved vulnerable is his decision to bequeath two Red Sea islands, Tiran and Sanafir, to Saudi Arabia during a visit by the Saudi king last year. That decision caused a nationalist backlash that led to rare public protests and litigation in the Egyptian courts.
But the election of President Trump, who has lavished praise on Mr. Sisi, has given heart to Egyptian officials. During a phone call in January, Mr. Trump invited Mr. Sisi to the White House. Since then, Egyptian ministers have been preparing for the trip, as well as a list of requests.
“With Trump in power, they feel they are assured that everything will be fine,” Ms. Mahdi, the analyst, said.
With the silencing of Mr. Sadat in Parliament, Hussein Gohar, an official with another opposition party, said politics had become a dispiriting and perilous pursuit in Egypt. “Honestly, I never know what will happen next,” he said. “Every time I travel abroad, I never know whether they will stop me.”