A person or group who provides resources and support for the project, program, or portfolio and is accountable for enabling success.
Merriam-Webster Online Dictionarysponsor (noun)
one who presents a candidate for baptism or confirmation and undertakes responsibility for the person's religious education or spiritual welfare
one who assumes responsibility for some other person or thing
a person or an organization that pays for or plans and carries out a project or activity , especially one that pays the cost of a radio or television program usually in return for advertising time during its course
to be or stand sponsor for