Pete Buttigieg, who recently rocketed to the top of polls in Iowa, released a $500 billion college affordability plan today, which would make public college tuition free for households earning under $100,000 and inject $120 billion into federal Pell Grants.The big picture: It contrasts with more expansive proposals from Bernie Sanders and Elizabeth Warren, who want to wipe out all college tuition and debt — though nearly every 2020 contender has their own ideas.The WashPost's editorial board called Buttigieg's plan "the most progressive" among 2020 Democrats "because it is more affordable and better targeted."Why it matters: College affordability is set to be a key issue in 2020 as the American electorate undergoes a distinct shift — with millennials and Generation Zers making up 37% of eligible voters.Gen Z is set to surpass the Silent Generation in voter share for the first time, a significant milestone as those new voters skew heavily liberal and are almost half non-white.College students turned out to vote at double the rate in the 2018 midterms than in the 2014 cycle — a trend that seems likely to continue in 2020.By the numbers: The class of 2018 graduated with a record average of $29,200 in loans for a bachelor's degree, but the issue of college debt affects a wider swath of the country than just current students and recent graduates.Americans over 60 hold $86 billion in college debt, brought on by financing their kids' education or going back to school after the 2008 financial crisis.The cost of college is also depleting rural America of its best and brightest as debt-saddled graduates head to major cities to find better-paying jobs.The bottom line: Buttigieg, as a moderate millennial Midwestern mayor, seems uniquely suited to speak to the issue of college affordability, and that opportunity is arriving just as he peaks in the polls.He has made the impact of automation on Rust Belt jobs a key campaign issue — plus, the 37-year-old and his husband have $130,000 in outstanding college debt between them.Go deeper: Buttigieg to face frontrunner scrutiny after surprise Iowa poll