After graduating from the University of the West Indies, Manning worked as a geologist with Texaco Trinidad Ltd., until he ran for Parliament in 1971.

The UNC and the NAR united in a coalition and formed the government; Basdeo Panday replaced Manning as prime minister.

The 2001 elections ended in a tie, with both the Opposition PNM and the governing United National Congress winning 18 seats.

Despite this the economic ratings of the country came in for high praises mainly from the Standards and Poor report on 15 August 2008 which raised Trinidad and Tobago from an "A−" to an "A".

The Government of Trinidad and Tobago also hosted King Juan Carlos I and Queen Sofia of Spain on 30 November to 2 December 2008.

[10] The Chilean president Michelle Bachelet paid Prime Minister Manning and the Government of Trinidad and Tobago a visit in 2010.

Some of his crime detection and prevention methods included the introduction of the Special Anti-Crime Unit of Trinidad and Tobago (SAUTT), two surveillance airships (commonly referred to as blimps), and the inclusion of six high speed off-shore patrol vessels for better control of the country's maritime borders and coastlines on 15 February 2010.

[citation needed] On 9 April 2010 Prime Minister Manning advised President George Maxwell Richards to dissolve Parliament resulting in a general election to be held two years sooner than was constitutionally mandated.

Manning and the PNM lost the election to The People's Partnership (UNC, COP, TOP, NJAC, MSJ).

Following the defeat, Manning officially resigned as Political Leader of the Party on 27 May 2010 but remained as the Parliamentary Representative for San Fernando East.

[citation needed] Manning was sent to the Privileges Committee following statements he made in Parliament on 19 November 2010, during a debate on the Interception of Communications Bill.

On 24 November 2010, Speaker of the House Wade Mark ruled that a prima facie case of contempt or breach of privilege had been made out against Manning and referred the matter to the committee for consideration.

Diagnosis of acute myeloid leukemia[11] was confirmed on 30 June 2016 and he died at 8:15 AM on 2 July 2016 at the San Fernando General Hospital,[12] at age 69.