Americans go to the polls Tuesday to choose 435 members of the House of Representatives, 33 members of the Senate and 36 governors. By the day's end, they will learn the general contours of the Republicans' margin of power in the House, the profile of the people occupying the states' governor's chairs, and – maybe, but not certainly – whether the Republicans have captured control of the Senate and thus hold power over the legislative branch of the nation.
The maybes come in two dimensions. The Republicans are in a strong position to topple the Democrats from power in the Senate but their triumph is not yet assured. And even a strong Republican tide might not bring the struggle for the Senate to a conclusion. The race in Louisiana may not be decided until a run off Dec. 6, and the race in Georgia could go into a run off Jan. 6.
Even so, Tuesday night will provide real suspense for political watchers on both sides of the 49th parallel – more than 500 political contests across a wide continent (and up to Alaska and over to Hawaii). Here's what to look for:
A country as big as the United States can experience as many as four atmospheric systems at one time, so discount the weather, which affects how many voters troop to the polling stations, and concentrate on the climate, which is changing dramatically in the nation.
Here's one manifestation: The older voters who used to be a dependably Democratic bloc now trend slightly into the Republican range. They vote in great numbers in all elections. Younger voters, a foundation of Barack Obama's political coalition, are far more Democratic now. They come out in presidential election years but not so much in midterm years. Very few of them will vote Tuesday – a big Republican advantage.
Indeed, the Democratic turnout disadvantage is so dramatic that last week Mr. Obama was urging supporters in campaign crowds to rouse their "lazy uncles" and get them to the polling stations.
Political scientists have talked about realignment and polarization for a quarter century, even as statistics examining both elements have bounced around. But this much is incontrovertible: Republicans are conservatives and Democrats are liberals.
That may seem obvious, or simplistic, but it was not always so. A Pew Research study this year showed almost no ideological overlap between the two parties—a fundamental departure from American politics only a generation ago.
Then there is the matter of political intensity and consistency, important measures for students of politics. Two decades ago, only 8 per cent of politically engaged Democrats could be considered consistent liberals. Now the figure is almost five times that high (38 per cent). Only a decade ago, only 10 per cent of politically engaged Republicans were consistent conservatives. Now the figure is 33 per cent.
The politicians are moving with the people. A Republican Senate in 2015 would have a far more conservative character than the Republican Senate did in 1981, when the GOP grabbed control of the chamber in the Ronald Reagan election.
But this much is clear: Whether controlled by Republicans or Democrats, the Senate in 2015 will have no Republican members remotely as liberal as some of the Republicans in the Reagan-era Senate, including Lowell P. Weicker Jr. of Connecticut, Charles Mathias Jr. of Maryland, Robert Stafford of Vermont, or Bob Packwood and Mark O. Hatfield of Oregon. All five of them departed Washington long ago, and their brand of Republicanism is all but extinct.
Mr. Obama's approval ratings have been on a slow slide since the middle of last month, reaching the 41 percentage level as the midterm congressional elections approached. Even more dangerous for the Democrats are clear indications that recent events – the offensive against Islamic State militants, the response to Ebola – have hurt the party, with 53 per cent of voters saying this fall's news events have made them feel less favourable toward the party, according to the Wall Street Journal/NBC News Poll taken in mid-October. Many Democratic candidates have been running away from Mr. Obama's embrace all autumn, but in contests where the candidate is closely identified with the President, the Democratic contender's prospects are dimming.
For an early evening indication of how things are going, keep an eye on New Hampshire, where Democratic Senator Jeanne Shaheen is fighting to be re-elected, and North Carolina, where Democratic Senator Kay Hagan is in a close re-election battle. If both fall, the Democrats are in for a long night – and, very likely, an even longer two years in the minority in the Senate.
The most intriguing Midwestern races are in the farm states of Nebraska (where the long-time Republican incumbent is fighting for his life against an Independent supported by many Democrats); Iowa (where a long-time Democratic seat is in danger of falling into Republican hands); and South Dakota (which has an unusual three-way contest that includes a former Republican senator running as an Independent).
In the South, the race to watch is in Arkansas, where a Democratic incumbent, Mark Pryor, is depending in part on Bill Clinton, not Mr. Obama, in an uphill battle for re-election. And out West, races in Colorado and Alaska are ones where the Democratic incumbents' chances are rated as toss-ups.
The likely result
A long evening of entertaining viewing is likely on Tuesday, with Mr. Obama's agenda, the character of American politics for the next two years and the atmosphere for the 2016 election all at stake. Stay tuned. But make sure you grab the most comfortable chair in the room. You'll be there a while.