The poll, sponsored and financed by Radio Africa Group, shows Ruto would beat Raila in Mombasa if elections were held today.
Asked whom they intend to vote for in the August 9 presidential vote, 41.9 per cent of respondents said they would go for the DP against 37.5 per cent who prefer a Raila candidature.
Mombasa — seen as the capital of the Coast region — has been Raila's political bastion for over a decade.
In the 2013 elections, for instance, Raila secured 69.7 per cent of the votes in Mombasa against President Uhuru Kenyatta's 23.7 per cent.
Ruto also remains the man to beat in three Mt Kenya counties surveyed, including Nakuru, the poll shows
In Nakuru, Ruto would win the presidential vote by 46.2 per cent followed closely by Raila at 32.8 per cent.
This is however an improvement for Raila who secured only 17 per cent of the Nakuru vote in 2013, against Uhuru's 80 per cent.
In populous Kiambu county, Ruto would garner 55 per cent of the presidential vote. Raila would get 23.1 per cent.
In Nyeri, 55.5 per cent of respondents said they would vote for Ruto against Raila's 19.6 per cent.
Raila however has a comfortable lead in Nairobi. The former Prime Minister would secure 48.2 per cent of the votes against Ruto's 37.6 per cent.
The polls were conducted between May 4 and 8 using SMS-based interviews. The sample size varied from county to county but was weighted to reflect the IEBC register of voters.
For the Mombasa gubernatorial contest, former Nairobi Governor Mike Sonko (Wiper) could upset ODM's Abdulswamad Nassir.
According to the poll, if elections were held then, Sonko would win by 45.6 per cent against Abdulswamad's 31.5 per cent.
UDA's Hassan Omar comes a distant third at 12.1 per cent.
The poll also suggests Governors Lee Kinyanjui (Nakuru) and James Nyoro could lose to UDA in the elections.
The two are among Mt Kenya governors who have stuck with Raila.
In Nakuru, the poll shows that Senator Susan Kihika would win the gubernatorial contest with 54.5 per cent against Kinyajui's 34.1 per cent.
In Kiambu, UDA's Kimani Wamatangi would win by 25.9 per cent with Nyoro coming a distant fifth with 11.6 per cent.
Coming closer to Wamatangi is former Governor William Kabogo at 19.7 per cent followed by Gatundu South MP Moses Kuria at 14.3 per cent.
In the fourth position is Patrick Wainaina Wa Jungle at 11.6 per cent.
In Nairobi, Johnson Sakaja and Polycarp Igathe are neck-to-neck, although the latter is hardly a month in the gubernatorial race.
The poll puts Sakaja ahead by 46.6 per cent against Igathe's 41.3 per cent.
For the senate seat, ODM secretary general Edwin Sifuna would win by 54.8 per cent of the votes against Bishop Margret Wanjiru who would get 25.3 per cent of the votes.
In Nyeri, incumbent Governor Mutahi Kahiga could secure a decisive victory. The poll shows he would win by 48.1 per cent against Senator Ephraim Maina who would secure 15.5 per cent of the votes.
