I think Salon touches on this question nicely with this article from last December about Trump Supporters.
In effect : There is no ACTUAL threat to the vast majority of Conservatives by Democrats or Liberals. There is only PERCEIVED threat, and that perception has been placed there over decades by Conservative media who have made a fortune by demonizing Democrats/Liberals and creating the divide we have today.
Why do Conservatives see politics as a win-at-all-costs war? Because Conservative media has spent decades convincing them that:
Fiction : Liberals want abortion legal as birth control.
Fact : Liberals want abortion to remain a legal option of last resort, especially in cases of rape, incest and where the health and well-being of mother and/or child are in danger. Most liberals are well aware of how modern birth control works and have no desire to use abortion as such, and organizations like Planned Parenthood, the boogeyman of the Conservative Christian Right, actually teach modern birth control, sexual health and family planning to prevent the need for abortion as an option among the underprivileged.
Fiction : Liberals want to take away all our guns.
Fact : Liberals like guns too! The vast majority of American gun owners are good responsible people. Hunting is not a crime, neither is sport shooting or gun collecting. The fact is that tighter regulation on who can purchase guns and how they purchase them does not impact responsible gun owners in the slightest, and only serves to remove methods by which people who should not be purchasing guns can currently do so. Tighter gun regulation won’t prevent criminals from having guns, and it won’t prevent all incidents of school/workplace/public gun violence, but if it prevents even a single incident from happening, it’s worth it.
Fiction : Liberals want America to become a Communist/Socialist state.
Fact : Only when it comes to healthcare and education. I have yet to meet an average liberal who seriously thinks we should be giving up our freedoms and individuality in exchange for government housing, three squares a day and the security of knowing Big Brother is always watching. That’s ridiculous. What liberals do want is a single payer healthcare system modeled after successful systems in Europe and Canada that treat everyone at the same level and don’t bankrupt families if someone has the misfortune to be diagnosed with cancer. What liberals also want is a reformed Education system that gives all K-12 students equal opportunity to succeed and then gives those willing to move on to higher education a path to do so without indebting themselves for 20+ years afterwards. That’s not Communism nor true Socialism, and the fact is that it would benefit every American equally (by design) no matter their ideology.
Fiction : Liberals want to live in a nanny-state where the Government controls everything and tells you what to do and how to think, and anything counter to that is met with violent oppression.
Fact : Oh, you mean like Conservative Christianity, or modern day Republican Conservatism? Yeah, that would be bad!
Combine all of that misinformation with constant repetition about how liberals are all elitist atheist assholes who think they’re better than the working class god-fearing conservatives and just want to take our tax money and give it to the lazy poor people and immigrants in exchange for their votes and you end up with an army of pissed off Americans who think the other half of the country is out to get them. Once you have achieved that level of discontent, which Conservative Media did during the Obama Administration, it’s pretty easy to mobilize those folks to go out and vote directly against their own best interests under the guise of “winning” the war against the “libtards”.