And the perceived success or failure of those policies and programs tends to determine how the parties' candidates, even those who don't support many of them, do at the polls.
This has been especially true in the past two decades, in which fewer Americans have been splitting their tickets or changing their minds from election to election than was the case from the 1950s to the 1980s.
For years, white Southerners voted Republican or for a third-party candidate in presidential elections and Democratic in congressional and state contests. Now they're solidly Republican.
For most of the 20th century, New York was a target state in elections, and Vermont was the most Republican state in the nation. Now they're both hugely Democratic.
These are things to keep in mind as the political air swirls with talk of Barack Obama as a Democratic Ronald Reagan annihilating the Republican Party.
Neither of our two political parties is going to be annihilated. Both have suffered far worse defeats than Mitt Romney and the Republicans suffered in 2012.
Both have figured out how to adapt and win over voters who used to vote against them -- or at least to position themselves to win when the other side's president is seen to have massively failed.
The 2008-2012 Obama campaign -- it never really stopped -- did an excellent job of turning out just enough voters to win 332 electoral votes in 2012. But Obama carried just 26 states to Romney's 24, which is relevant when you look at future senatorial elections.
As for House elections, Obama carried only 207 congressional districts to Romney's 228. That's partly because Republicans had the advantage in redistricting after the 2010 census.
But it's also because Democratic core constituencies -- blacks, Hispanics and gentry liberals -- tend to be clustered geographically in big metropolitan areas. Obama's large margins there helped him carry many electoral votes, but not so many congressional districts.
And Obama's in-your-face liberalism, so apparent in last week's inaugural speech, antagonized some groups in a way that may hurt Democrats for some time to come.
The Obamacare contraception mandate helped Romney carry 59 percent of white Catholics -- probably their highest Republican percentage ever -- and 79 percent of white evangelical Protestants. Those groups total 44 percent of the electorate.
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