CHARLOTTE, N.C. — On a precarious political bridge, Democrats are desperately trying to reach a promising future before their old foundation crumbles behind them.
Union clout has eroded. But Hispanic strength is growing, raising long-term hopes. What about now?
The party survived the mass exodus of Southern conservatives, nearly all of whom are now Republicans. That left labor unions as a backbone of Democratic activism, providing crucial foot soldiers and volunteers in countless elections. But steady and long-running attrition among American unions is one big reason Democrats have few realistic hopes of regaining control of the U.S. House this fall and are battling to keep their grip on the White House and Senate.
The chief bright spot in the party's future may still be several years away. Minority populations, especially Hispanics, are growing at a much faster rate than whites, and they lean heavily toward Democrats, partly because of Republicans' stern approach to immigration.
President Barack Obama lavishes attention on his party's traditional base, including union households, as well as on the up-and-coming minority constituencies. But it's not clear whether the shift in influence from the old blood to the new is progressing fast enough to save the president from a bad economy and a well-financed Republican opponent, Mitt Romney.
The Democratic Party "is in a period of transition," said Simon Rosenberg, president of the New Democrat Network, a Washington think tank. It's shedding remnants of the New Deal coalition, which relied heavily on labor unions and city political machines, and adapting to a global economy, the rise of social media and "geopolitical challenges."
"The Democrats are still crossing that bridge," Rosenberg said.
John J. Pitney Jr., a political scientist at Claremont McKenna College, said the transition presents campaign challenges for Obama and other Democrats on the ballot this fall.
"With urban machines long gone and public employee unions in possible decline, who will run the phone banks and precinct walks?" Pitney said. "Ideological activists are one potential source."
Some polls, however, find considerably less enthusiasm this year among Democrats and Democratic-leaning independents than among Republican voters.
More than a third of all U.S. workers were union members in 1954, but that figure now is below 12 percent. Federal, state and local government employees have much higher union membership rates than do private-sector workers. But the sagging economy has triggered heavy state-government layoffs in many places, weakening those unions.
As union membership falls, however, Hispanic communities are growing. The U.S. Hispanic population grew by 43 percent from 2000 to 2010, accounting for more than half of the entire nation's population increase in that decade. And for now, at least, Hispanic voters lean Democratic.
"As we look to the future, demographics play in our favor," said Tom Daschle, the former Senate Democratic leader. Hispanics are the main reason, he said, but "Asian Americans are increasingly in our camp" as well.
When Democrats in Charlotte stop basking in their bright demographic future, they might question why they are struggling in many congressional races.
Americans tell pollsters they see Democrats as better able than Republicans to look out for the middle class and to handle health care, Social Security and issues "important to you and your family." Yet Democrats fear that the Republican wave from 2010 that heralded a GOP-controlled House and gains in the Senate might not have crested.
Indeed, the clout that Democrats enjoyed in 2009 — when they held the White House, the House and, for a time, a filibuster-proof Senate majority — is in danger of being completely reversed on Nov. 6.
Republicans fully expect to maintain their House majority. And they have a shot at winning control of the Senate.
Republicans hold a 241-191 edge in the House, with three vacancies. Democrats and their independent allies hold 53 of the Senate's 100 seats.
The limping economy and high unemployment rate are the main reasons the president is struggling, and Republicans are tying Democratic lawmakers to him in some key states.
Some Democrats say the GOP, and its tea party wing in particular, are handing them opportunities on numerous fronts. But they wonder if their party is nimble enough to exploit them.
For example, polls show that most Americans support Obama's bid to end a decade-old income tax break for the richest households. Romney and congressional Republicans adamantly oppose it.
"They've got ideological blinders on," said Rep. Chris Van Hollen, D-Md.
But some Democrats say Republicans have done a better political job on the subject, successfully packaging their anti-tax, anti-Obama message for voters.
"The Democrats haven't been as adept at selling their strategy to the public," Rosenberg said.
The three-day Charlotte convention gives Obama and other Democrats a high-profile chance to do better in the campaign's last two months, even as they hope demographic trends will help them in future elections.