America’s young adults, who twice helped propel President Barack Obama to victory at the ballot box, are mostly planning to stay home in this year’s elections.

A survey by Harvard University’s Institute of Politics shows that young adult voters in the U.S. are less motivated than at any time in at least 14 years, with fewer than one-in- four saying they’ll definitely cast ballots in November’s midterm congressional races.

Worse, for Obama and Democrats seeking to maintain the party’s control of the Senate, is that young Republicans are more interested in voting than are young Democrats.

“There’s an erosion of trust in the individuals and institutions that make government work -- and now we see the lowest level of interest in any election we’ve measured since 2000,” said John Della Volpe, the institute’s polling director. “We will likely see more volunteerism than voting in 2014.”

Just 23 percent of those ages 18 to 29 say they definitely plan to vote -- 8 percentage points lower than what Harvard recorded during a similar time before the 2010 midterm elections, when Republicans won control of the U.S. House.

Among the most likely youth voters, the poll found traditional Republican constituencies more enthusiastic than Democratic ones, with 44 percent of those who backed Republican Mitt Romney in the 2012 presidential election saying they’ll definitely vote, compared with 35 percent of Obama voters.

“A lot can be done between now and November,” said Trey Grayson, the institute’s director. “But it does show that motivation is going to be a problem for younger voters, who tend to trend a little more Democratic.”

In 2008, Obama won 66 percent of the vote from those ages 18 to 29, exit polls showed. Four years later, in his re- election bid, he carried 60 percent of the age group’s vote.

One positive finding for Democrats: The poll shows young adults are somewhat less disillusioned with the Obama presidency than five months ago, with his approval rating at 47 percent, up from a historic low for the poll of 41 percent.

Obama’s approval is boosted by stronger support from Hispanics and blacks. Among young whites, his approval rating is 33 percent.

The survey’s findings underscore the challenges that Obama, 52, and Democrats face as they seek to block Republicans from gaining the six seats needed to take control of the Senate.

Democratic efforts to maintain their hold on the chamber are burdened by low approval ratings for Obama and his health- care law as well as demographics favoring Republicans because midterm electorates tend to be older and whiter than in presidential years.

Democrats, who are defending more seats than Republicans, are fighting history because the White House’s partisan allies have lost ground in the Senate in 12 of 17 midterm elections since the end of World War II.

When looking at two potential top 2016 presidential candidates, young voters have vastly different views of Democrat Hillary Clinton and Republican Chris Christie.

Fifty-two percent have a favorable view of Clinton, a former U.S. secretary of state, while 42 percent have an unfavorable view. Among the 62 percent of young Americans who’ve heard of Christie, just 21 percent have a favorable view of the New Jersey governor, while 39 percent hold an unfavorable view.

Falling trust in public institutions and cynicism about elected officials is partly driving the youth apathy. During the past year, trust in the president has decreased to 32 percent from 39 percent; the U.S. military has seen its level of trust drop to 47 percent from 54 percent, and the U.S. Supreme Court has fallen to 36 percent from 40 percent.

Wall Street is trusted to “do the right thing” all or most of the time by 12 percent of young Americans, roughly the same percentage as in previous Harvard polls.

Voting rates among young adults, those 18 to 24, fell to 38 percent in 2012 from 44.3 percent in 2008, according to a U.S. Census Bureau report released last week. That followed increases in two consecutive presidential elections in 2004 and 2008.

The Harvard survey also found that political party affiliation plays a role in social network preferences. Twitter and Tumblr are platforms preferred by young Democrats, while young Republicans are more drawn to Pinterest.

The survey of 3,058 residents, ages 18 to 29, was taken March 22 through April 4 and has a margin of error of plus or minus 1.8 percentage points on the full sample.