Secondly, it could lead to a string of damaging congressional investigations being launched by House committees controlled by the Democrats, on everything from Mr Trump's tax returns to the business interests of his family. Sherrod Brown is easily expected to win re-election even in a state Trump carried two years ago, but the open governor's race is a much tighter contest.
Senate Majority Leader Mitch McConnell, R-Ky., and other GOP leaders have also been blaming Social Security and Medicare as sources of the ballooning deficit, suggesting cuts and other reforms could be coming if they hold control.
The party of a first-term president tends to lose congressional seats in off-year elections. Donaldus Magnus is driving everything left and right, Republican and Democrat.
Stirring fear of foreigners and trumpeting American nationalism worked for Trump in his 2016 election victory against the Democrats' establishment candidate Hillary Clinton. Democrats were buoyed by a wave of Republican retirements and an overwhelming fundraising advantage.
Should Democrats fail tomorrow, the argument about what kind of progressive party they should be will start again.
Since Donald Trump entered politics the Democrats have struggled to compete.
Democrats are favoured by election forecasters to pick up the minimum of 23 House seats they need for a majority, which would enable them to stymie Trump's legislative agenda and investigate his administration. "We can't have that", he said in an ABC interview. In another early race to watch, retired Marine fighter pilot Amy McGrath took on three-term Rep. Andy Barr in the Kentucky district that extends beyond Lexington.
This year the two groups combined have turned out 38 percent of the vote, far lower than the overall county average. "It's an awakening of the Democratic Party". The Democrats stand little chance of winning the Senate, but with this new breed of candidate they could take control of the house. Failure would leave them unable to check president Trump's power.
In other words, the GOP could actually expand their control over the Senate by quite a bit.
The final polls varied, but they were generally good for Democrats.
Those who believe in the dire message, particularly white conservative voters in the middle of the country often derided as flyover territory because it is so alienated from the more liberal, progressive, and economically vibrant coastal areas, are expected to vote Republican.
Despite not being on the ballot, Trump made the midterm elections about him.
"The reasonable range of outcomes in the Senate still seems fairly wide, with a bigger GOP gain possible, or no gain at all or even a Democratic gain", they explained.
Democrats boasted record diversity on ballots.
Hitting three states in one day, with a final late rally in Cape Girardeau, Missouri, Trump hammered home his boast that "the Republican agenda is the American dream". "We'll vote for fantastic candidates all over the country - including a historic number of women - who want to raise wages, fight for justice, and help more people get health care". "You're going to see the largest gender gap we've ever seen". "We need to elect politicians who believe in it and will do something about it". The demographic shifts also reflect each party's closing argument.
But Democratic former President Barack Obama hit the campaign trail in the election's final days to challenge Trump, questioning his policies and character.
Support for the president has not, however, automatically translated into support for Republicans. California, with a population of 40 million has two Senators, as does Wyoming, which has less than 600,000 people. You go back to 2001, 2000, they think they got jobbed when the Supreme Court stole the election in the Florida recount away from Algore.
While Donald Trump is not on the ballot, the consequences for his presidency could be dramatic.