Asian-Americans are a fast-growing but still-overlooked segment of the American electorate , and a national survey out Tuesday finds their votes in the presidential election are still up for grabs.

Asian-American likely voters who have made up their mind in the presidential race favor Barack Obama over Mitt Romney by almost 2-1, but fully one-third are undecided. That's a finding in the National Asian American Survey, released by two University of California political scientists.

One in six Asian-Americans live in swing states, but they're not hearing from the campaigns.

"I think this is a huge missed opportunity, especially in a lot of battleground states going into an election that could be pretty close," says UC Berkeley scholar Taeku Lee.

Lee found diverse views and surprising shifts. Vietnamese-Americans, who have had long ties to the Republican Party, are now mostly undecided. Meanwhile, Filipinos are moving from the Democrats to the GOP.