What's at stake in Tuesday's vote

Considered to be on the political ropes just two years ago, U.S. Republicans are now poised for a comeback in Tuesday's midterm elections.

With all 435 congressional seats, 37 Senate seats and 37 governorships in play, the Republicans are widely expected to deliver a stinging defeat to the Democrats, in the process dealing a blow to the agenda of U.S. President Barack Obama.

If the advance polls prove correct, the midterm vote on Nov. 2 would represent a significant reversal of political fortunes.

In 2008, the Democrats gained full control in Washington. They expanded their presence in Congress, reached a near filibuster-proof majority in the Senate and, of course, won an historic presidency.

Now, most polls are forecasting that the Republicans will be able to take enough of the 100 or so seatsthat could change hands in the House of Representatives and re-establish control.

That would mean that the powerful position of Speaker, now held by California Democrat Nancy Pelosi, would switch over to a Republican, most likely minority leader John Boehner of Ohio.

If they win, Republicans would also take control of key House committees and be able to launch investigations.

Pledge to America

If the GOP's recent Pledge to America campaign document is any indication of future plans, the Republicans would also move to extend the Bush tax cuts for high income earners (which the Democrats want to let expire at the end of this year), cut government spending by $100 billion and repeal parts of Obama's health-care law and financial regulations.

To make all this happen, the Republicans would probably need to control the Senate, which may not happen.

But they seem assured of some gains there and are tipped to win the majority of the 37 governorships up for grabs, with victories predicted in such Democratic "blue states" as Michigan, Wisconsin and Pennsylvania.

What changed for the GOP? Mostly, voter frustration with high unemployment, high government debt and the ailing economy.

But the Republicans, for the most part, were also able to muster a mostly unified opposition to Obama's controversial health-care bill and stimulus package.

In this, they had help from the Tea Party phenomenon, which has provoked some commentators to accuse the Democrats of suffering an "enthusiasm gap," especially in comparison to the invigorated, fiscally-conservative Tea Party movement that seems to have tapped into the discontent over government spending.

The political climate is such that even long-time Democratic stalwarts are facing tough re-election challenges.

Senate Majority Leader Harry Reid is at serious risk of losing in Nevada and Massachusetts Congressman Barney Frank, the chairman of the House financial services committee, which took centre stage in examining the bank bailouts, is being seriously challenged by Iraq-war vet Sean Bielat.

Key Tea Party races

During the primaries, enthusiastic Tea Party groups opposed certain established Republican candidates, accusing them of losing their way. This led to splits on the right, which will be of prime interest to analysts on election night.

For example, in the race for a Senate seat from Florida, Tea Party favourite Marco Rubio is taking on Charlie Crist, the former Republican governor of the state, who lost the primary challenge to Rubio and decided to run as an independent.

Another Tea Party-backed candidate, Republican Sharron Angle has a good shot of beating Senate Majority Leader Harry Reid in what would be a major coup of the GOP.

The Republicans are also pinning their hopes on Tea Party-backed Rand Paul, son of Texas Congressman Ron Paul, who is up against Democratic rival Jack Conway in Kentucky.

Paul sparked a national controversy at one point by suggesting that he may not have supported the Civil Rights Act of 1964.

Other Tea Party candidates have also been dogged by controversial statements throughout their campaigns.

Indeed, a number of Republicans slammed the nomination of controversial Senate candidate Christine O'Donnell in Delaware, saying they had a better chance of picking up the seat had they chosen Mike Castle, a moderate Republican.

O'Donnell, who gained national attention with her past comments on witches, is not even close to her rival in pre-election polls.

Generally, however, Republicans have embraced the Tea Party movement as an invigorating breath of fresh air andTuesday's resultsshould bebe able to rendersome sort ofverdict on how much the movement either helped or hurt Republican fortunes.

Other key races

Other key races include Illinois, where the Senate seat may be more popular at least symbolic than the two men vying for it. Obama held it before he became president and it gained notoriety after former governor Rod Blagojevich was accused of trying to sell it off to the highest bidder.

In this contest, Republican Mark Kirk has a good chance of defeating Democrat Alexi Giannoulias.

Another high-profile Democrat in trouble is three-term Wisconsin Senator Russ Feingold, known for his independence and willingness to buck his own party. Feingold currently trails Republican Ron Johnson, a plastics manufacturer.

But not all may be bleak for the Democrats. They are still expected to maintain a majority of seats in the Senate. And it would be considered a big victory for them if they could win the governorship in two of the biggest states.

In Florida, Democrat Alex Sink, the chief financial officer of the state, is in a close battle with Republican Rick Scott, a health-care executive.

Meanwhile, in California, former governor Jerry Brown, the Democrat, appears to have a solid lead over former eBay CEO Meg Whitman.

What price victory?

Of course, if the Republicans do perform as well as expected Tuesday, their victories and control over Congress will come with a price.

If the economy continues to stagnate, the Republicans would no longer be able to pin all misfortune on the Democrats.

Obama will also be given a new target when he is up for re-election in 2012: He will be able to blame obstructionist Republicans for any measure he was unable to pass.

Losing the Houseon Tuesday will be seen asa blow to his presidency, but is in no way a predictor of his political survival in 2012.

In 1982, Republicans suffered huge losses in the House, but former president Ronald Reagan went on to pummel his rival two years later.

Similarly, the Republicans took control of the House and the Senate in the 1994 midterm elections, but former President Bill Clinton went on to win re-election after that.

Mark Gollom is a senior writer with CBCNews.ca.