[5] Messina became President Obama's White House deputy chief of staff and earned the nickname "the fixer.

He graduated from Boise High School in 1988 and earned his Bachelor of Arts degree in political science and journalism from the University of Montana in 1993.

[14][15] In 1993, as a college senior, Messina managed Dan Kemmis's successful re-election bid for mayor of Missoula, Montana.

[20] Messina has also been involved with other political campaigns from Alaska to New York, including serving as an advisor to Montana state senator Jon Tester's successful election in 2006.

In January 2011, Messina left his job at the White House and began "a rolling series of personal seminars with the CEOs and senior executives of companies that included Apple, Facebook, Zynga, Google, Microsoft, Salesforce, and DreamWorks".

[30] "Whereas British pollsters consistently missed that the Tories were moving into pole position, Messina's internal numbers showed for weeks they were on course to be the largest party.

[34] In January 2016, Messina was hired by Prime Minister of Italy Matteo Renzi as campaign's advisor for the constitutional referendum in December.

[37] In June 2016, Messina began working with Spanish prime minister Mariano Rajoy,[13] using data and targeted social media that ultimately helped Rajoy win a bigger than expected victory in that year's elections and take charge of a minority government in October of that year.

[38] Messina worked with Prime Minister Theresa May as a campaign strategist for the 2017 United Kingdom general election.