Bristol West MP Thangam Debbonaire is asking people to vote on the charity she will donate to after running the London Marathon.
She wants her constituency to have the final say on which organisation, from a shortlist of three, should receive the money she raises through sponsorship.
Hundreds of suggestions came from the public when they were asked to help.
The Labour MP then whittled them down to three Bristol charities which support breast cancer screening, vulnerable children and wildlife.
What are the charities?
BUST - Breast cancer Unit Support Trust - BUST is nearly three quarters of the way to raising the £1million needed for a dedicated MRI scanner for the Bristol Breast Care Centre at Southmead Hospital. Thangam herself received treatment for breast cancer at the centre. The scanner will also be used to scan for prostate and bladder cancers.
Bristol Drugs Project's Youth Group - This free youth group supports children who are living with a parent or family members struggling with alcohol or drug-use. It gives young people respite from a difficult home life, allowing them to take part in activities that their parents are often unable to coordinate or afford. The charity estimates at least one child in every Bristol classroom is affected by a parents' drug and alcohol use.
Avon Wildlife Trust's My Wild City project - The project's community initiatives in Thangam's constituency have already created mini nature reserves in gardens, streets, schools and businesses. The project aims to make Bristol a more pleasant place for all creatures.
The MP is running the marathon in April because, after overcoming cancer, she said she is now "very conscious" of the need to take her health "much more seriously".
The former professional musician was diagnosed with breast cancer in 2015 and endured eight months of intensive treatment before returning to parliamentary work in 2016.
People in Bristol West have until midnight on Saturday 2 March to vote. The London Marathon will take place on 28 April.