In most of the 2012 primaries and caucuses, youth turnout – defined as eligible voters from 18 to 29 years of age – has been in the single digits. In Nevada, one percent of under-30s voted, and in Virginia, two percent turned out. In the bellwether state of Ohio, youth turnout was somewhat better at 7%, but the number dropped significantly from the 25% rate in 2008.

Former Massachusetts Governor Mitt Romney – who is just shy of securing his party’s nomination after Tuesday's five primary wins and Wednesday's announcement from former House Speaker Newt Gingrich that he intends to suspend his campaign next week – has improved his showing with young Republicans compared to 2008, but he has hardly closed the deal with them.

Earlier this month, Romney won Maryland’s primary easily but lost the state's youth vote to Rick Santorum and barely edged the former senator in Wisconsin.

Throughout the 2012 Republican primary season Rep. Ron Paul has attracted a dedicated group of young supporters who kept him competitive in some of the early states, but he has drawn fewer than 200,000 total youth votes in all the states with exit polls up to this point. In a comparable set of states from the 2008 primaries, Barack Obama attracted more than twice as many young votes.

Sen. John McCain’s youth support was remarkably low in 2008: he took just one third of the under-30 vote, the lowest in history.

Romney has an opportunity to do better, but the primary turnout numbers and his share of the youth vote offer no signs that he has energized young people yet.

If the Republicans lose the youth vote by a landslide margin in two consecutive presidential elections, they should worry that the party is losing a whole generation for the long term.

Meanwhile, the president’s popularity has slipped among youth, but he remains more popular than not within the demographic group. Last month, three different national polls (conducted for CNN, McClatchy and Reason Magazine) put his youth popularity rating between 61% and 63%.

As the president worked this week to court young voters, and Romney answered the president’s call with his own campaigning to young people, the question is whether either can draw significant numbers in November.

Romney has nowhere to go but up compared to McCain’s 2008 effort. Polls show young people tilting liberal on some environmental and social questions, such as gay rights, yet they are highly skeptical of the federal government as a tool for economic reform.

Earlier this week, the Public Religion Research Institute and the Berkley Center for Religion, Peace, and World Affairs at Georgetown University released a survey of 18- to 24-year-olds that asked them to rate various groups on a scale from 1-100. The Christian Right scored in positive territory at 54.1, Occupy Wall Street was below the midpoint at 44.5, the Tea Party was a little lower at 41, and the federal government in Washington scored worst of all at 40.9.

There is clearly room for a Republican campaign to make inroads with young people.

Youth remain a strong constituency for the president’s reelection, given his personal favorability and also the liberal tilt of young people on social issues.

But turnout will be key.

The presidential reelection campaign cannot be satisfied with energizing the same people who voted for Obama in 2008, because approximately 12,500 young people turn 18 every day, and most citizens under the age of 25 were too young to register or vote in 2008.

Registering new voters will be a special challenge since many states have made the process more difficult. New voter registration laws that require government-issued photo IDs or impose rigid regulations on the volunteers who register voters add another hurdle to getting young people on the rolls and to the polls.

Most states prevent eligible voters from registering during the very period when interest in a campaign reaches its height, the last month before an election. What business would require you to sign up for its service months in advance and then appear in person at a particular location during limited hours to obtain it?

That is no way to encourage political participation in a great democracy, and it’s one reason that U.S. turnout is usually the lowest among all the developed democratic countries in the world.

In 2008, for the first time in decades, more than half of young adults turned out, which seemed to show the political world that the Millennial Generation was engaged, but since then their participation in the democratic process has been rocky.

In the Massachusetts Senate election, just 14 months after the '08 election, only 15% of eligible young adults voted (compared to 57% of older citizens).

In the national midterm elections of 2010, youth turnout was weak at 24%.

This doesn't necessarily mean that young voters have lost their enthusiasm for political engagement. Instead, it reminds us that turnout rates vary dramatically, depending on how each election is fought, the investment of the major campaigns in youth outreach, the ease or difficulty of registering in various states, and the issues that receive the most attention.

For the likely Republican presidential nominee, Mitt Romney, however, the lesson ought to be clear. Take the election to young people, talk about their issues and concerns, and give them significant roles in the campaign. The future of the Republican Party could depend on it.

Peter Levine is Director of Research and Director of CIRCLE (Center for Information & Research on Civic Learning & Engagement) at Tufts University’s Jonathan M. Tisch College of Citizenship and Public Service