Egyptian President Abdel-Fattah al-Sisi is running virtually unopposed in this week's elections after a series of potentially serious candidates were arrested or withdrew from the race under pressure.The vote will be the least competitive of the three presidential elections held in Egypt since the 2011 uprising ended Hosni Mubarak's 29-year reign and raised hopes of democratic change.Al-Sisi's only opponent is Moussa Mustafa Moussa, a little-known politician who supports the president and has made almost no effort to campaign against him.Here is a look at more serious contenders who failed to make the ballot.Ahmed ShafiqA former air force general and Mubarak's last prime minister, Shafiq lived in self-imposed exile in the United Arab Emirates since shortly after finishing a close second in the 2012 presidential election won by the Islamist Mohammed Morsi. In December, he was deported from the Emirates, a close Egyptian ally, and flown back to Cairo after he announced he intended to run. He was met at the airport by unidentified security men and whisked away to a suburban hotel. Government representatives persuaded him to abandon his presidential ambitions, raising the specter of legal proceedings over alleged corruption during his tenure as civil aviation minister, according to numerous, unconfirmed reports.In January, he said did not believe himself to be the "ideal" man to lead the country at this stage.Sami Annan The former general quietly served as the military's chief of staff under Mubarak, drawing national attention only in the 17 months of military rule after Mubarak's ouster. As the deputy head of the then-ruling Supreme Military Council, he negotiated the transfer of power to Morsi in June 2012.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. Two months later, Morsi removed him. In January, he announced his intent to challenge al-Sisi and posted a video on social media that berated the president for involving the military in civilian affairs and urging civilian and military institutions to stay neutral in the race. On January 23, the military detained him over charges that included incitement against the armed forces and forgery.Khalid AliThe prominent rights lawyer was the last potentially serious challenger until January 24, when he announced he was quitting the race. He complained that authorities targeted his supporters and that poor Egyptians had been bribed by al-Sisi loyalists to sign documents supporting his candidacy. His own supporters faced delays and intimidation at notary offices, where they needed to register 25 000 "recommendations" for him to qualify as a candidate. A key left-leaning figure in the 2011 uprising, Ali had the potential to win protest votes and revive interest in street politics by fellow "revolutionaries" whose ranks have been depleted by imprisonment, exile or marginalisation.Mohammed Anwar SadatThe former lawmaker said he quit the race because the climate was not conducive for campaigning and because he feared for the safety of his supporters. A nephew of Egypt's assassinated leader Anwar Sadat, he was thrown out of parliament amid allegations of leaking sensitive documents to foreign diplomats.Ahmed KensowaThe army colonel declared his intention to run, only to be court-martialed and convicted of breaching military regulations prohibiting political activism. He was sentenced to six years in prison in December.