"The only question would become would those gains be large enough to change the majority, to put the Democrats out of power in the House and/or Senate," Mann said, predicting Republican gain in the range of 35 to 50 seats in the House. The party needs a net gain of 39 seats to regain control.

Things are, however, murkier in the Senate. Recent polls are showing several key races are getting closer, and the Democrats are spending heavily to defend their majority in the upper chamber.

Unlike the House, which holds elections on all its seats every two years, the Senate holds elections on a third of its 100 seats every two years. This year, 37 Senate seats are up for grabs, and 10 of them are considered contested. With but one exception, the contested seats are now in Democratic hands, and Republicans have to gain 10 seats to have the Senate majority, a task viewed as extremely difficult, if not improbable.

"It's possible they'll take control (of the Senate), but it would be an astonishing night if they did," said Politico's Alexander Burns.

"We know it's going to be a big change, but we don't know just how big," said Mann.

In order to keep the Republican wave at bay, the Democratic party has been using the White House megaphone to get their message out. President Barack Obama and First Lady Michele have been campaigning tirelessly for the Democrats from coast to coast.

But the Republicans are already plotting the post Nov. 2 scenarios. Mitch McConnell, the Senate Republican leader, told the National Journal "the single most important thing we want to achieve is for President Obama to be a one-term president," drawing ire from the White House.

"There will be more Republicans. We are ready to work together. The question is, are they ready to work with us?" senior Obama adviser David Axelrod told MSNBC.

William Galston of the Brookings Institution commented that the elections seem all but certain to reshape the political landscape, with the Republicans deciding how to use their increased power, and the Democrats determining how best to defend what they accomplished in the previous Congress.