The scorecard for the Democrats was bad, very bad, although it certainly could have been worse. A loss of about 64 seats in the house of representatives, for a Republican majority of about 61 — the biggest partisan turnaround in more than 60 years, but still a smaller majority that the Democrats had going in. A loss of six seats in the senate, for what looks like still being a 53-47 majority (slightly better than expected), and the loss of probably 10 or more governorships, including critically important ones such as Michigan, Ohio and Pennsylvania.

Perhaps the most important thing to understand about this result is that it was very much in line with expectations. Its effect on what happens over the next year or two will be limited by the fact that it was already factored into most people’s calculations. So, it will not so much create legislative deadlock as confirm a deadlock that was already there; it will not so much push Barack Obama to be more conciliatory as confirm the conciliatory course on which he was already set.

In this it differs from previous milestones such as the Democratic takeover of the Senate in 2006 or the Republican takeover in 1980, neither of which was widely expected. Even the most obvious precedent — the Republican victory in both houses in 1994 — surprised many observers, certainly by its dimensions.

It’s also worth remembering that there’s nothing historically odd about the presidency and congress being controlled by different parties. For 40% of the 20th century the incumbent party was in a minority in the house, and for most of that time in the senate as well. Four successive Republican presidents — Nixon, Ford, Reagan and Bush snr — never had a house majority, and only Reagan ever won the Senate (and even he lost it again before his term was up).

Sometimes presidents and legislators from different parties manage to work together. Often they don’t. Gerald Ford in his 2½ years as president vetoed 66 bills; Harry Truman in less that eight years vetoed 250. Going back further, Grover Cleveland in his first term vetoed an extraordinary 414. Obama so far has vetoed only two. Expect that number to rise.

For all that, the system continues to work, in its creaky, 19th-century way. Congress can check the president, but most of what he does can continue unaffected without legislative interference.

And as Clinton’s example shows, a hostile congress is no bar to success, re-election and historical vindication.

Although their electorates are nominally the same, there are many reasons why presidential and congressional elections produce different results. Turnout in the mid-terms is lower, and low turnouts are skewed towards older and whiter voters. The by-election atmosphere tends to produce swings against the president’s party that often fail to hold up in the longer term. The advantages of incumbency can play out differently in house, senate and presidency. And the looseness of party discipline means that many members may have major differences even with a president of their own party — many of the house Democrats who lost yesterday had already conspicuously distanced themselves from Obama.

The great realignment in American politics happened over a 30-year period, from 1964 to 1994, when the white southern electorate deserted the Democrats following passage of the Civil Rights Act. The Republicans gained the upper hand in the electoral college — it became an article of faith that only a southern Democrat could win the presidency, a complete reversal of the previous position — and eventually, as incumbents retired, that advantage filtered through to congress as well, culminating in the landslide of 1994.

In 2006-08 the Republicans started to suffer the consequences of that realignment after southern influence pushed the party so far to the right that it became unelectable in large swathes of the north and west.

Yesterday’s results have put a pause on that trend, but they have not yet halted it. If the wilder elements in the Republican Party have their head, they may ultimately just end up reinforcing it.