Sri Lankans head to the polls Wednesday with the ruling Rajapaksa brothers looking for a super-majority in parliament to change the constitution and unravel democratic safeguards.

Political observers say the siblings -- renowned for their ruthless crushing of Tamil separatist rebels to end a decades-old conflict in 2009 - want to end presidential term limits, bring the judiciary and police under their direct control, and extend their dynastic power to a new generation.

The Rajapaksa political dynasty, a long-time force in Sri Lanka, dramatically stormed back to power in November when former defence secretary Gotabaya, 71, was elected president.

Mahinda Rajapaksa (left) and Gotabhaya Rajapaksa (right) are looking to strengthen their grip on Sri Lankan politics
Mahinda Rajapaksa (left) and Gotabhaya Rajapaksa (right) are looking to strengthen their grip on Sri Lankan politics AFP / Ishara S. KODIKARA

Gotabaya -- a former army officer dubbed "The Terminator" by his own family -- won comfortably running on a law-and-order ticket while capitalising on government infighting.

He swiftly appointed as prime minister his older brother, Mahinda, the former strongman president ousted in 2015 after a revolt within his own party and a public backlash against alleged nepotism and corruption.

A big victory in this week's parliamentary polls would allow them to overturn constitutional changes passed by the previous administration to decentralise power and prevent another strongman from emerging.

"What we will end up with is an elected authoritarian regime," analyst Kusal Perera told AFP.

Supporters of the Rajapaksas' party attend a campaign rally ahead of the upcoming parliamentary elections, near the capital Colombo
Supporters of the Rajapaksas' party attend a campaign rally ahead of the upcoming parliamentary elections, near the capital Colombo AFP / LAKRUWAN WANNIARACHCHI

Both Rajapaksas have argued that a return to the concentration of power in the hands of the president is needed for them to rebuild the island nation.

"Vote for our party to revive the economy, build a disciplined society and take the country in the right direction," the 74-year-old Mahinda told thousands of supporters at his final rallies in the south of the country late Sunday.

Presidential term limits were introduced in 2015 under former president Maithripala Sirisena when parliament approved sweeping constitutional amendments.

Mahinda Rajapaksa was ousted as president in 2015 after a revolt within his own party
Mahinda Rajapaksa was ousted as president in 2015 after a revolt within his own party AFP / LAKRUWAN WANNIARACHCHI

Those changes also made the judiciary, police, civil service and election commission independent branches of government.

If the Rajapaksas' party secures a two-thirds majority in parliament, they will be able to sweep away those reforms.

Sri Lankan soldiers stand guard in 2009, towards the end of the decades-old separatist conflict which the Rajapaksas are renowned for ending
Sri Lankan soldiers stand guard in 2009, towards the end of the decades-old separatist conflict which the Rajapaksas are renowned for ending HO / PEDRO UGARTE

Rights campaigners warn that intimidation and threats against lawyers, activists and journalists have already escalated under the Rajapaksas.

"A campaign of fear has intensified since the 2019 presidential election, and has cast a shadow over the 2020 parliamentary election campaign," Human Rights Watch said.

Gotabaya in February issued a veiled warning to the judiciary in a speech where he said judges should refrain from "unnecessary interference" in the political process.

The Rajapaksas, who are revered by their majority Sinhalese for defeating the Tamil Tigers and ending the separatist conflict, are widely expected to secure a big win on Wednesday.

The opposition has also been badly weakened by internal rivalries and, with the economy in tatters, the brothers' populist messages are resonating with voters.

Even if their party fails to secure a two-thirds majority, they could defy a law that prevents MPs from crossing the floor and "buy" opposition legislators to form an alliance.

"But that would send a powerful message to the international community that the government is not interested in the rule of law," political analyst Victor Ivan told AFP.

Also waiting in the wings is Mahinda's 34-year-old legislator son, Namal.

Sri Lanka watchers believe Mahinda may want Namal, a rising star in his family's party, to eventually take over the presidency.

However, there is another important constitutional change from 2015 -- due to take effect after Wednesday's elections -- that could lead to a power struggle between the brothers.

That change will transfer some of the president's powers to the prime minister, and veteran politician Mahinda might not want to give the powers back to "The Terminator" after getting them.

"The constitutional structure creates conditions for a power struggle between the prime minister and the president after this election," Ivan said.

"One of them will have to take a step back or else we will see a showdown."