From now through Election Day, CBS News chief political consultant Marc Ambinder will provide his keys to understanding the state of the campaign:
1. The House seems to be holding fine for Republicans. There are a ton of Democratic incumbents at or below 45%. In a wave election, nearly all of those folks lose. In 2006, there were a ton of GOP incumbents polling between 46%-48% -- many of them lost. Note: If the Republicans only were to win the 48 seats that voted for a Democrat for Congress and McCain for President, they'd pick up 48. Even if Democratic enthusiasm matches Republican enthusiasm, the game board is tilted towards Republicans.
On the flip side, there is evidence that African Americans are becoming more engaged and more interested in voting. Given that they vote 90% or so for Democrats, having their base get more motivated -- even late -- means something.
Of course, most of the House battleground districts have low African American percentages, so it is less of a boon than in other situations.
2. The Senate landscape still tilts towards Republicans -- the polls look particularly strong in Arkansas, North Dakota, Indiana and Wisconsin. Republicans are also positioned to win four of the five open seats they're defending - Florida, New Hampshire, Ohio and Missouri. That leaves eight races -- Republicans needs six of these -- Kentucky, Pennsylvania, Illinois, California, Washington, Colorado, (where polls show a Bennet surge of late), West Virginia and Nevada. Republicans have an edge in West Virginia and Nevada among these seats.
4. In Florida, Democratic early vote results, particularly among voters with "No Party Affiliation" listed, roughly matches the pace of 2006, which Democrats find encouraging.
5. Republicans think their advantage in the Michigan governor race will swing the roughly five competitive CDs in that state their way. No real signs in Texas that Bill White is going to pull off an upset over Rick Perry in Texas. Republicans are very nervous about a late Tom Tancredo surge in Colorado.
6. For the White House, the big three Senate races are Delaware, Illinois, and West Virginia, along with Alaska, given Lisa Murkowski's alienation from her party. The thoughts here are on the lame duck session, both because of legislative initiatives like the START treaty (which Obama views as critical to show the world that he can get tough things done) and the legitimacy of the session itself. There's no question that Republicans will question the very idea of a rump session, and you can expect the GOP echochamber (Limbaugh, Hannity, with assists from Fox News, Palin, etc.) to threaten to punish members of Congress who show up for the lame duck.
The Atlantic's Marc Ambinder is CBS News' chief political consultant. You can read more of his posts in Hotsheet here. You can also follow him on Twitter.