As the electrifying, no-holds-barred battle for Congress in the 2018 midterm elections campaign comes to a close, Democrats appear poised to win back the House of Representatives.

Ramping up the drama, a slew of tightening polls indicate that the Senate might also drift away from Republicans if all the dominoes fall towards the opposition party on Tuesday.

While polling analysts still forecast the Senate to remain in GOP control, some surveys indicate nail-biting contests in key states in the final days before Nov. 6. In wave elections, close races often end up tilting the same way - that is what Democrats hope for this year.

In the Senate battle in recent weeks, Republicans have been confident of winning North Dakota but concede that Nevada and Arizona could go to the Democrats, making the chamber evenly balanced on 50 seats each but still in GOP control because of the tie-breaking vote of Vice President Mike Pence.

That, however, was before new polls in Tennessee - the "firewall" state for Republicans - dead level. If Democrats cling on in Florida, Missouri and Indiana, where their incumbents have faced tough fights and an energized Republican base loyal to President Trump, then it could all come down to the Volunteer State.

Here are what some crucial polls say ahead of Tuesday's midterm elections:

Blue wave warning for the House

Though Democrats face some hurdles in the House, the majority of pollsters believe the odds are in favor of a "blue wave." Democrats need to flip 23 seats to take control of the lower chamber. Last week, Dave Wasserman, who is House editor of the nonpartisan Cook Political Report, said their forecast was being updated, predicting that Democrats gain 30-40 seats, up from 25-35 seats.

On Sunday, CBS News said it ran three scenarios for the House and shared its findings. The best scenario for Democrats showed 225 Democratic seats to 210 Republican seats. However, with a margin of error of plus-or-minus 13 seats on each side, even in the best-case scenario, Democrats winning the House isn't a sure thing.

Another survey, the final ABC News/Washington Post pre-election poll, shows Democratic House candidates leading Republicans 52 percent to 44 percent among likely voters. But the Democratic lead has closed from 14 percentage points in August and 13 points in October to now just eight points.

Senate likely to remain red, but...

Some individual races are looking tighter than ever in the waning days of the 2018 election cycle - and they are mostly moving towards the Democrats.

Among the tightest Senate races to watch are:



Florida : Gov. Rick Scott, R, is leading incumbent Sen. Bill Nelson, D, in a new poll released Saturday. The results from St. Pete Polls give Scott a lead of 49.1 percent to 47.5 percent. But that is within the margin of error, with 3.4 percent undecided. That latest poll was the first for some time to put Scott ahead.

: Gov. Rick Scott, R, is leading incumbent Sen. Bill Nelson, D, in a new poll released Saturday. The results from St. Pete Polls give Scott a lead of 49.1 percent to 47.5 percent. But that is within the margin of error, with 3.4 percent undecided. That latest poll was the first for some time to put Scott ahead. Tennessee : Rep. Marsha Blackburn, R, is in a dead heat with Democrat Phil Bredesen. On Friday, East Tennessee State University and Targoz Strategic Marketing released two separate polls that showed Blackburn and Bredesen tied. The ETSU poll found 44 percent of likely voters saying they supported each candidate, and in the Targoz poll, 48 percent of likely and early voters supported both Blackburn and Bredesen. Republicans had previously thought that Tennessee was moving out of Bredesen's reach.

: Rep. Marsha Blackburn, R, is in a dead heat with Democrat Phil Bredesen. On Friday, East Tennessee State University and Targoz Strategic Marketing released two separate polls that showed Blackburn and Bredesen tied. The ETSU poll found 44 percent of likely voters saying they supported each candidate, and in the Targoz poll, 48 percent of likely and early voters supported both Blackburn and Bredesen. Republicans had previously thought that Tennessee was moving out of Bredesen's reach. Texas: An Emerson battleground poll found incumbent GOP Sen. Ted Cruz holding a slim advantage with 50 percent support. His Democratic challenger, Rep. Beto O’Rourke has 47 percent, and 2 percent said they undecided. The GOP is still favored but O'Rourke appears to be closing the gap in a state where he shouldn't have a. prayer.

An Emerson battleground poll found incumbent GOP Sen. Ted Cruz holding a slim advantage with 50 percent support. His Democratic challenger, Rep. Beto O’Rourke has 47 percent, and 2 percent said they undecided. The GOP is still favored but O'Rourke appears to be closing the gap in a state where he shouldn't have a. prayer. Missouri: In a shock poll from Saturday, incumbent Democratic Sen. Claire McCaskill and Republican challenger state Attorney General Josh Hawley are tied at 47 percent among likely voters. Until that poll, Republicans had been increasingly confident of picking up Missouri - an outcome that almost certainly would have ensured they held the Senate.

While picking apart specific polls indicates the Democrats moving towards what once seemed an elusive victory, forecaster FiveThirtyEight remains unconvinced the opposition party will pull it off, stating Sunday that Democrats have only a one-in-seven or 15.3 percent chance to take control of the Senate. Republicans have a six-in-seven chance, or an 84.7 percent chance to retain Senate control. But everyone remembers how wrong such forecasts turned out to be in 2016.

Tennessee in particular will be one to watch. Republicans view Tennessee as a "firewall" state protecting them from the loss of the chamber. With the current balance of power 51 to 49 and Democrats looking highly likely to lose North Dakota, the GOP could afford to lose Arizona and Nevada while failing to pick up Florida, Missouri or Indiana and still survive with 50 seats and Vice President Mike Pence's casting vote. That calculation would be swept away by losing Tennessee.

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Republicans hold a 51-49 majority in the Senate and 26 Democratic senators are up for re-election on Tuesday, compared to just nine Republicans. Of the 26 Democrats, 10 are running in states President Trump won during the election in 2016.

Here is RealClearPolitics' roundup of Senate polls.

A wide-lens look at Congress

Overall, Democrats hold a seven-point advantage over Republicans in the final national NBC News/Wall Street Journal poll.

Fifty percent of likely voters say they prefer a Democratic-controlled Congress, while 43 percent want Republicans in charge. It's a slight drop for Democrats, who in October had a nine-point advantage. Among the wider pool of registered voters who were polled, Democrats lead Republicans by six points, 49 percent to 43 percent.

FiveThirtyEight puts Democrats ahead in its overall generic poll, which is based on polls that ask people which party they would support in an election. Democrats lead Republicans, 50.5 percent to 42.4 percent.

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Morning Consult and POLITICO also surveyed registered voters to ask if they want Congress to be controlled by Republicans or Democrats. In that poll, Democrats are up eight points on Republicans, 46 percent to 38 percent.

RealClearPolitics has a comprehensive list of all overall Congressional polls here.

What top politicians are saying

Vice President Mike Pence told The Hill last week that he believes Republicans will keep control of the House. President Trump told reporters Sunday that Republicans will "likely" do well in the House, while his "primary focus" has been on the Senate - sentiments that some Republicans viewed as the party accepting the House would slip from its grasp.

Sen. Chris Van Hollen, D-Md., who is chair of the Democratic Senatorial Campaign Committee, told "Fox News Sunday" that the Democrats have a “very narrow path” to retaking the majority in the Senate, but offered a downbeat assessment of their chances of pulling it off.