Over the last decade, America’s youngest voters have been characterized as disaffected, disconnected and unreliable when it comes to casting a ballot.

But the presidential election has turned that notion on its head. Youth turnout — which was larger than the historic year of 2008, when it was dismissed as an aberrant phenomenon — has cemented the “millennial” vote as one of the key demographics that candidates can no longer ignore.

The groundswell didn’t just happen. It was the result of concerted efforts by civic activists across Florida and other states who worked to get out the vote among a generation that is too often written off as apathetic. At the University of Florida, the Bob Graham Center for Public Service spearheaded a registration effort using TurboVote, an interactive platform developed at Harvard University that allows students to register online, update their voting information or request an absentee ballot with ease.

The Graham Center’s effort resulted in 3,428 registered users at the university. It was one of 10 institutions, including Florida International, Miami Dade College and the University of Miami, using TurboVote in the state. Collectively these institutions registered 11,090 TurboVote users. Those numbers make a huge difference in a state where a recount decided the presidency in 2000 by 537 votes.

More important, if the pattern holds, that means that 20-somethings’ views on everything from war and peace to student loans and same-sex marriage will matter every bit as much as senior attitudes on Medicare and Social Security. A 2011 Civic Health Index co-authored by the Bob Graham Center noted that candidates traditionally skirt youth voters and their issues because of their underrepresentation at polling places.

So expect more candidate visits to college campuses and campaign commercials with faces that look like the most diverse generation in American history.

And candidates should not dismiss this as something to worry about only in presidential election years. There’s mounting evidence that America’s youth are mobilized and ready to weigh in on local and state issues in off-year elections, too.

Consider:

• With 50 percent of eligible voters under 30 casting ballots, the 23-million-strong millennial wave grew as a share of the electorate from 18 percent in 2008 to 19 percent this year. They now are larger than the proportion of voters over the age of 65 (17 percent, according to the National Exit Polls conducted by Edison Research).

• In Florida, Ohio, Pennsylvania and Virginia, if Romney had won half the youth vote, or if young voters had stayed home altogether, he would have won those key battleground states. But President Obama won the majority of youth votes over Gov. Romney by 60 percent to 37 percent, according to the Center for Information on Civic Learning and Engagement (CIRCLE) at Tufts University.

• In Florida, Obama’s margin among young voters increased over 2008 as well: That year, he won young voters 61-37, but this year CNN’s exit poll showed him winning the age group 67 to 31 percent.

• The youth vote also was cited as a factor in a key Florida state election: the defeat of Republican Rep. Chris Dorworth — the first would-be House Speaker to lose a general election since 1988.

“What we’re seeing today is two demographic trends that are pushing the state back toward the Democratic Party,” said Lance deHaven-Smith, a past president of the Florida Political Science Association and dean of Sunshine State political analysts . “The millennials are a larger age cohort than the baby-boom generation, and they are quite liberal on taxes, gay marriage, environmental protection and more.”

Peter Levine, director of CIRCLE at Tufts University, adds “Youth turnout of around 50 [percent] is the ‘new normal’ for presidential elections. Considering that there are 46 million people between 18 and 29, this level of turnout makes them an essential political bloc.”

Shelby Taylor is communications director of the Bob Graham Center for Public Service at the University of Florida.