Predictions

Although I study public opinion, that doesn't give me any special insight as far as election predictions are concerned.  With public opinion on any topic, there are lots of questions you can and should consider, and differences of a few percent either way don't matter much.  But with elections, there's only one question that matters--the choice of candidates--and differences of a few percent are important.  Moreover, the results don't depend on public opinion, but on the opinions of the voters.  So predicting elections involves questions about predicting who will vote and identifying and adjusting for relatively small "house effects"--tendencies for particular polls to over- or under-estimate support for different parties--and then you have questions about translating votes into seats.  Still, it's fun to try, so here are my predictions:

Senate 51R-49D

House  235R-200D

In this election, people are also concerned about how the outcome will affect the future of democracy.  The study of public opinion should provide some insight into that.  There are several reasons for optimism:

1.  An independent judiciary with a long accumulation of precedent.   Trump and his allies lost almost all of the lawsuits that they filed over the 2020 election.

2.    Bureaucracy.  There are a lot of agencies that have routines which are based on a combination of laws, regulations, and tradition.  Even if political officials want them to change direction, they will continue to try to follow those routines.  The routines generally involve following relatively impersonal rules, so bureaucracies usually resist demands to "reward friends and punish enemies" or manipulate statistics to make the party in power look better.  This is connected to point 1--in many cases, routines are based on an interpretation of legal requirements.

3.  Political culture.  Americans don't generally take to the streets to protest.  After the 2006 election in Mexico, their were several months of protests by supporters of the defeated candidate, Andrés Manuel López Obrador.  According to Wikipedia,  "López Obrador and his supporters began organizing mass protests, marches, and civil disobedience, culminating in a massive rally in Mexico City's historic Zócalo on 30 July 2006. Estimates of the crowd at the rally range from 500,000 to 3,000,000 supporters.[34] Additionally, López Obrador's campaign set up plantones, or encampments, inside the Zócalo and along Paseo de la Reforma, one of Mexico City's main arteries, for 47 days and slowing traffic for hours."  Estimates of the number at Trump's January 6 rally range widely, but the upper end seems to be 80,000, and that was a one-time event--there were no mass protests before or after.  This is also connected to point 1:  even people who wanted to overturn the results of the election focused on legal or quasi-legal efforts like "forensic audits."  At some level, Americans have a lot of respect for the political and legal system:  the remedy for injustice is appeal to some higher authority (real or imagined) rather than violent resistance.

On the other side, there is a reason for pessimism:  the complexity of the American electoral system provides a lot of opportunities to spread doubt about unfavorable results and manipulate the rules to the advantage of your side.  So people can undermine democracy without taking a definite stand against it--in fact, they can undermine democracy while imagining that they are upholding some higher value (like the rule of law or the Constitution).  Also, long tradition, combined with the difficulty of constitutional amendments, makes it hard to make changes in election procedures--e. g., attempts to have more uniform standards for elections are denounced as "a federal takeover," and reforms like multi-member districts are not even considered.

The result is that there is little danger of a coup, or the suspension of elections, or jailing of opposition candidates.  But there is serious danger that government will continue to be ineffective and unresponsive, or even get worse.