Washington, Nov 3 (DPA) Republicans were projected to win a series of early races as polls closed in US congressional elections Tuesday that were likely to deal a major blow to President Barack Obama's Democrats.

All 435 seats in the House of Representatives and 37 seats in the 100-member Senate are up for grabs as well as 37 governorships and many state and local positions.

Republicans, who would need to gain 10 seats to win control of the Senate, picked up two seats held by Democrats in Indiana and Arkansas, according to early projections.

The party also held seats in Florida and Kentucky, two early victories for the grassroots Tea Party movement that has energized the conservative base.

But Democrats did manage hold on to some key Senate seats that could wind up leaving them in control of the upper chamber, even with a much smaller majority.

West Virginia's sitting Governor Joe Manchin was projected to defeat Republican business magnate John Reese in a closely-fought race.

Chris Coons was declared the winner in Delaware, defeating Tea Party-backed candidate Christine O'Donnell and holding the seat once held by Vice President Joe Biden. Democrats also held Connecticut, with Richard Blumenthal defeating Linda McMahon, the former manager of World Wrestling Entertainment.

Polling suggests Republicans are highly likely to gain more than the 39 seats they need to reclaim a majority in the lower House, buoyed by the support of independent voters who helped put Obama in office two years ago.

Initial exit polls found that the still-sluggish US economy was the top concern for 62 percent of voters, according to pollster John Zogby, with many angry at Obama's massive spending plans and a weak labour market. Unemployment sits at 9.6 percent.

"Obama didn't have any strategy. It has been a great disappointment," said Susan Allen, in her 60s, as she cast her vote in New York City.

In a last-minute bid to stem the losses, Obama made a round of radio interviews with such popular personalities like Ryan Seacrest, of American Idol fame.

"I want everyone to remember that you can't shape your future if you don't participate," Obama said on Seacrest's syndicated show. "You've got to get out there and vote."

With many neck-and-neck races across the country and ballots counted across six time zones, it will likely be a long night before final results are known. Some races could take days to sort out.

The Republican Party's takeover of Congress, together with the Tea Party's uncompromising stance on most political issues, has many predicting legislative gridlock during Obama's next two years in office leading up to the 2012 presidential elections.

Polls have shown major dissatisfaction with incumbents from both parties. "Dump Incumbents" signs peppered the streets in and around Washington.

In Florida, Republican Marco Rubio was projected to win over sitting Governor Charlie Crist, a former Republican who launched an independent campaign for the Senate seat.