COLOMBO, Sri Lanka — Even before the coordinated bombings that killed 250 people last month, Sri Lanka’s president and prime minister were in trouble — largely of their own making.

Now calls for President Maithripala Sirisena and Prime Minister Ranil Wickremesinghe to step aside when their terms are over, if not before, are mounting from opposition groups as well as from the ranks of their own parties.

A member of Mr. Wickremesinghe’s party issued a public letter last week, asking the prime minister to make way for new leadership. Then, on Tuesday, a small opposition group in Parliament initiated no-confidence votes against both leaders, citing their failure to act on intelligence warning that an attack was imminent as well as their leadership in the aftermath.

The calls for accountability coincide with jostling for an upcoming presidential election, and they seem to have all but crushed the chances for both men, senior officials, party members and analysts said in interviews.