The first national elections since Trump captured the White House in a stunning 2016 upset will be a referendum on the polarizing Republican president and his hardline policies, and a test of whether Democrats can turn the energy of the liberal anti-Trump resistance into victories at the ballot box.
Stirring fear of foreigners and trumpeting American nationalism worked for Trump in his 2016 election victory against the Democrats' establishment candidate Hillary Clinton.
Democrats' chances to pick up seats have improved in key races in Georgia, Pennsylvania, California and Washington, according to ratings changes by Cook's David Wasserman. Forecasting website FiveThirtyEight gave Democrats an 88 per cent chance to win the House, Republicans an 81 per cent chance to keep the Senate.
"What can we learn, if anything, about where this vote is coming from?"
For months, Democrats have drilled their central message into the minds of voters: if Republicans strengthen their grip on Congress, they will destroy your health care, including coverage protections for people with pre-existing medical conditions.
Although unlikely, the Democrats could manage to flip the House of Reprenentatives and the Senate, taking full control of Congress. CBS News' current estimate is for Democrats to win 225 seats - just beyond the 218 needed for a majority - while Republicans win 210.
Even as networks refuse to run the ad, Trump still espouses the same message in it, often telling crowds at his rallies that the migrant caravan is full of unsafe people.
President Donald Trump speaks during a rally at Southern Illinois Airport in Murphysboro, Ill., Oct. 27, 2018.
"Democrats want to invite caravan after caravan of illegal aliens to pour into our country".
Sending thousands of troops to the US-Mexico border to counter a migrant "invasion", questioning the validity of birthright citizenship, and spreading stories of scandalous murders by undocumented immigrants: Trump and his Republicans are making immigration a closing argument of the campaign. "No nation can allow its borders to be overrun".
"Even though I'm not on the ballot, in a certain way I am on the ballot", Trump said.
Last week, Democrats led by three points, 47% to 44%.
White people and Hispanics, Republicans, suburbanites, men, the elderly, the college educated, and supporters of President Trump were the most likely to say they have faith in democracy now. When you participate in the political process, you can be a check on bad behavior.
Many people have already voted.
FILE - Florida Democratic gubernatorial nominee Andrew Gillum, left, and Senator Bill Nelson (D-FL), right, listen to former President Barack Obama as he addresses the media and supporters as they stump for votes at a rally in Miami, Florida, Nov. 2, 2018.
Some Democrats and Trump critics have long suggested the records would show the president is not worth as much as he claims.
Facebook said it had blocked 115 accounts for suspected "coordinated inauthentic behaviour" linked to foreign groups attempting to interfere in the midterm elections.
What they do ask is: Am I better off since Trump took office?
Well, I think it's a lot more complicated than that.
Another 36 states will also elect governors as well as numerous seats in their state legislatures. RealClearPolitics puts Trump's average approval at about 43 percent, with 53 percent disapproving. Along with these, a host of local posts are also up for elections in various states. "That is particularly true when a president is unpopular, as this president is".
The party of a first-term president tends to lose congressional seats in his first midterm.
Historically, though, Republicans are more reliable voters in midterm elections. "They could only go up. but we don't know where these ballots are going".
What makes it even more hard for the Democrats is the majority of the seats in these states were overwhelmingly in favour of Trump in 2016. "Anything that gets done will have to be a bipartisan basis".