1940's: Huge majority of voters registered as Democrats who hold White House for all of the decade and Congress for 8 out of 10 years.
1950's: Republicans win White House by nominating one of the great military heroes of the 20th century but are still a small minority of voters compared to Democrats who again hold Congress for 8 years. Republican Party stagnates as largely a me-too version of moderate Democrats.
1960's: Democrats hold White House for 8 out of 10 years. Nixon elected in reaction to how horrendously the Democrats screw up country both in terms of Viet Nam and domestic upheaval. Republicans still in minority but "Silent Majority" is voting with them.
1970's: Democrats regain power after (largely press fabricated) scandals and elect worst and most incompetent president in our history. Republicans still in minority but gaining ground.
1980's: Republicans hold White House for entire decade and Senate for most of it. Still in minority but the margin is reduced to a few percentage points.
1990's: Due to lackluster Republican presidential campaign and freakishly weird third party candidate Democrats manage to elect sociopathic "boomer" con artist to White House with 43 % of vote. Same candidate reelected with 49 % against weak opponent and same third party weirdo. But Republicans regain House for first time in 40 years and hold both houses of Congress for most of decade. They also draw statistically even in party registration by the end of the decade.
2000's: Intensely close election, reflecting 50/50 political divide, results in Republican White House, Senate, and House for the first time in almost a half century. First midterm election shocks Democrats as party in White House increases seats in both houses for only second time in US history. Democrats react by moving even further to the left of the electorate. Party affiliations begin to shift to Republican majority as voters notice Democrats espouse apologising and hiding from sponsors of first foreign military attack on American soil since Pearl Harbor. Republican president fights and wins two regional wars in unheard of time with fewer casualties than one week of Viet Nam and 70 % plus poll approval.
All in all guys, it's been a long struggle but the direction is in our favor. The depression and WWII generation is dying off. Boomers are entering early middle age and many are discovering common sense. Generations X and Y are noticably more conservative than their grey haired balding ex-hippy parents.
I may be a hopeless optimist, but this is honestly how I read the past fifty plus years.