Transcript for Key House and Senate races to watch

Now to a closer look at the state of the races that newly released ABC news Washington Post poll also showing. A narrower lead for democratic house candidates and on the senate side the GOP is working with a strong hand. ABC's chief national affairs correspondent Tom yeah Thomas is in our elections studio with the key races to watch Tom good morning. Whitmore do you and the gang over their wit on election night we're going to be tracking more than 500 races across the country all the house races 35 in the senate. And 36 races for governor let's start the house. This is the current make up for the house and when you look at the sport you look at the country you see there's a lot of red these are all Republican held districts they're the party in power. Out of all these races we've isolated more than a hundred we believe he's going to be the competitive races on election night in the house you can see so many vis a red. And you can see clusters in the northeast New York Pennsylvania but even in very red states like Kentucky Kansas and Texas. Nearly a dozen races in California remembered these are the competitive races into the suburbs the excerpts we believe this is where the battle's going to be for the house we've taken all these districts and we've lined up like this by poll closings and you concede this is why this is a race like we've never seen before. All these Republican districts on defense remember the key number and house is going to be 23. This is how many scenes the house the dense have to flip. In the house to become the party in power a couple of early races were going to be watching names you may be during early the night Katie McGrath in Kentucky you think Kentucky red state what's going on here she's a former fighter pilot Democrats are really excited about her she's taking on congressman Andy Barr the incumbent here but here's the key number right here the president won this district big but Democrats believe in her and they believe they're gonna they're gonna turn out for her under the big race for watching here Barbara Comstock the the incumbent. Battle tested out of the suburbs of Virginia this is what she's up against this is a district that Hillary Clinton won. Democrats feel very comp and about this went and that we go to south quarter write your board a 26 portal school Berle. Also battled tested in district that Hillary Clinton won big corals have. Distance himself from president trump on immigration. And tax issues we'll see what happens in Florida as he moved to the senate it's a much different story here you can see there's a lot more blue Democrats and a pretty much more seats and as we go to the map there's fourteen races that were watching closely here these are the key races we rule want to see what's going on. As we get the key races button. In the for the Democrats these are seats that Democrats currently hold. But that Republicans the president did very well at 4016 we're talking about states like. Missouri states like Montana and North Dakota to key races there and Indiana but Republicans are also on defense and a couple of seats here in Texas were talked about that race would dental Rourke in Texas also in Tennessee is well a big race there we'll see with a night goes where it. Tommy Thomas Forrest thanks so much very important point out some those districts to work Hillary Clinton won. That's of course were some Republicans are struggling absolutely. Our thanks Tommy Emma so much to talk about this morning so we brought in a ringer you may have heard this guy he's air chief anchor's name is George Stephanopoulos he's going to be hosting our special edition of this week later this morning as well as our election coverage on Tuesday night. Police are in our poll this morning gives Democrats. In the house and a point advantage. But that's not a lot. Not at all threat on the bubble whether or not the Democrats take control. The house for a couple reasons number one because it's a national. A Paulson that's capturing a lot of races a lot of sees where the Democrats have a huge advantage they in New York City. But if I have a 2530 point lead if you look at those battleground states that Tom pointed out right there to lead narrows considerably to about five points. Which is right very close the margin of error so this is going to be a nail biter all through the night on whether Democrats can take control of the house senate. Much higher than that much what charters Thomas pointing out right there which you're seeing there is Democrats trying to defend seats the trump went pretty big. In in 2016 North Dakota. Missouri Indiana. And then they only have a couple of chances to pick up seats Nevada and Arizona are the best chances. Theodore work a long shot in Texas so that you could even see a situation it's not impossible. On tees in NPC Democrats. Take the house for Republicans gain seats in the senate it if president trump is so unpopular 40% in our new poll. Which is historical. A low. Eight in this context wise it's not a blow up few reasons number one the economy is doing very very well right now the lowest unemployment. In years and I think that always helps the incumbent. Party right there number two even though the president. Is unpopular overall he's very popular. Among Republicans in unlike many mid term elections at least going into the mid terms on Tuesday the Republican paste doesn't appear to be. Depressed and they're getting they they they appear to be engaged ready to vote and that's holding up the president's numbers right now and Republican numbers right now. It's also has to do with the Matt he's very popular in the states where there are competitive races so he's he's closing strategy is rare. Very much into plea to the base he's been pretty hard edged done. As he likes to say the caravan to have an online order is this strategy knoller risky. Now they also where he's been can campaign finally she's really B campaign those races of the senate races that are deep red deep red states right now. That could consolidate. The Republican base in those states in one of things you've seen is that the Republicans are doing better on the issue. A border security. Right now the question for the president for his party is that gonna create a backlash in those suburban districts where Republican House members. Are in danger and that's what they have to worry about so if if he loses. The house of the Republicans lose the house what are the implications. For the next two years of the trump presidency when number one it stops the ability of of the president and Republicans to advance their agenda. Three unified has to say the number two it opens up the possibly the presence could be facing multiple investigations. On multiple fronts if you had a house majority. The subpoena power. They can look into questions not only about Russian interference in the last election but all kinds of oversight of president trump his administration his business is that's a brand new ball game. And a polarized America we could be heading into an era of even more polarization the question anger George Stephanopoulos appreciate it thank you very much. Our remind everybody George any ABC news political team here and have much more reporting and analysis on Tuesday's mid term elections coming up later this morning. On the special edition of this week from ABC news election headquarters which we're gonna unveil this morning. And be sure to join George for full coverage on election night George will be joined by our entire political team. Starting at 8 eastern on Tuesday night right here and ABC George thank you and I appreciate it.

This transcript has been automatically generated and may not be 100% accurate.