By Jennifer De Pinto, Anthony Salvanto, Kabir Khanna, Fred Backus and Jennie Kamin

It may not be easy for Democrats to take the House majority, as they have to win a string of districts in Republican territory and get strong turnout, but they head into Tuesday in position to do so — even if narrowly. CBS News ran three scenarios. Scenario one is our best estimate as of today: 225 Democratic seats — just beyond the 218 needed for a majority — to 210 Republican seats, with a margin of error of plus or minus 13 seats on each, keeping the possibility open that Republicans retain control.

Here's what voters are telling us: This is an important election. Democrats continue to benefit from both a large gender gap and a higher percentage of Trump voters supporting Democratic House candidates (approximately 6 percent) than 2016 Clinton voters crossing over to the Republican side.

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CBS News' polling indicates Republicans could save their majority by persuading these Trump voters to return to the Republican Party. In scenario two, Republicans reduce their crossover rate to match that of Clinton voters, which is closer to 3 percent. We estimate that Republicans would save about 10 of their seats from flipping in this scenario, giving them a total of 220 and Democrats the remaining 215, keeping the House in Republican hands.

If this were the case, Democrats would likely improve on their past performance, but fall short in many affluent suburban districts they are targeting. If seemingly vulnerable incumbents can survive in districts like NJ-7, TX-7, TX-32 and CA-48 on Tuesday, it will be an indicator Republicans could end the night with their majority intact.

This is no easy task. Among voters in key districts who tell us they already cast a ballot, crossover rates remain tilted in Democrats' favor: 5 percent among Trump voters, versus just 1 percent among Clinton voters so far.

The third scenario sees Democrats winning a solid majority in the House. This is equally likely in our model to the second scenario, in which Republicans hold the House. One way for Democrats to consolidate their lead is to win over more independent voters in key races. Such voters currently support Republicans by 5 percentage points. If enough independents vote Democratic, such that Democrats win this group, even narrowly, we estimate they would gain approximately seven additional seats, giving them 232 in all, or a 29-seat majority. In this scenario, Democrats are likely to pick off blue-collar districts that voted for Trump, such as KS-2, ME-2, or PA-10, and/or some suburban seats that currently look like longshots, such as FL-15, NC-9 or NC-13.

CBS News Battleground Tracker estimates are based on a statistical model combining what voters tell us in polls with characteristics of their districts. We interview more people in key districts that will decide the makeup of the House. We end up with a range of possible outcomes, which have consistently included narrow Republican holds and comfortable Democratic victories. Last month, we explored how different turnout scenarios could lead to each of these outcomes.

Perhaps spurring the large turnout expected this year, 93 percent of voters in battleground districts say their vote in this midterm election matters just as much — or more — as in a presidential election. Democrats and Republicans are equally enthusiastic about voting.

Democrats continue to maintain their edge in the race for control of the House of Representatives, due to strong backing from women, young voters and minorities. They are also relying partly on about 1 in 5 voters who have not voted in a recent midterm election. Republicans are getting support from white voters, older voters and those who usually vote in midterm elections.

More than 7 in 10 voters in these key districts continue to say their vote will be about President Trump, and that's split between those who say they'll vote for him (34 percent) and against him (38 percent).

Most voters think this election is important, but Democrats (34 percent) are twice as likely as Republicans (16 percent) to say their vote in 2018 matters more than a presidential election.

And more Democrats than Republicans say they will be angry if their party doesn't win control of Congress.

Democratic voters say their vote is about preventing things they don't want to happen over the next two years, but Republicans voters say their voting based on things they want to happen.

Most don't expect compromise in Washington if the Democrats win. About eight in 10 voters in these districts think if Democrats win control of Congress, their priority will be to investigate and try to impeach Mr. Trump, not work with him. Majorities of Democrats (67 percent) and Republicans (91 percent) agree on this.

In the closing days of the campaign, the president has put the issue of immigration front and center. Voters are divided on how they view the caravan of migrants from Central America who are making their way to the U.S. border. Most Republicans see it as a threat to the U.S., but most Democrats do not.

More voters approve than disapprove of the U.S. sending troops to the border. Support for sending troops is higher among those who see the caravan as a threat. But many of those who aren't sure if the migrants are a threat support troops at the border.

Immigration is a top issue for Republican voters, and it's even more important for those who view the caravan as a threat to the U.S. The issue has energized some Republicans. Those who see it as a threat are more enthusiastic about voting, compared to those Republicans who don't view the migrants that way. Nine in 10 Republicans say if Democrats win control of Congress they will be tough enough on immigration.

The issue of health care is an advantage for Democrats. Voters who say the issue is very important in their vote are overwhelmingly backing Democratic candidates for the House. Few voters in these districts say feel they have been helped by the changes Republicans in Congress made to health care laws.

More than 8 in 10 voters continue to say civility in politics is getting worse and that political violence is becoming more frequent. Majorities across the political spectrum agree on this, but there's disagreement about how the president handles the issue of political violence. Most Democrats disapprove, while most Republicans approve.

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The CBS News 2018 Battleground Tracker is a panel study based on interviews conducted of registered voters in 66 competitive and likely competitive congressional districts in the United States. The poll was conducted by YouGov, an online polling company. This poll was fielded between October 30-November 3, 2018 with 6,466 respondents. The respondents were selected from YouGov's online panels to be representative of registered voters in these districts in terms of age, race, gender, and education. The sample was weighted according to gender, age, race, and education, based on the American Community Survey, conducted by the U.S. Bureau of the Census, as well as 2016 Presidential vote, and post-stratified on district type. The margin of error (a 95 percent confidence interval) is approximately 1.6 percent.



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