so it's not necessarily the incumbent specifically who gets a boost at the finish, but whoever is trailing.

Well you'll be able to check it out in less than a month.

I'm not saying that it's impossible for an incumbent to pick up support as you describe, but it's far from the norm. Decades of research on what has been known as "the incumbent effect" points in precisely the opposite direction.

The incumbent is (usually) the known quantitiy. If voters were inclined to support him/her, they would say so in the polling. Most undecideds tend to break for the challenger, a 3rd party, or stay home.

It isn't 99.9%. It's high... but not that high (https://www.opensecrets.org/bigpicture/reelect.php)... and while a very high percentage of incumbents get reelected... a very high percentage of incumbents hold comfortable leads in the polling. We're talking about races where the incumbent trails in the polling or is very close.

in many cases even dead ones.

Sorry... that isn't the case. Incumbents that are dead even in the final polling are not more likely to be reelected than their dead-even status would indicate.

Nancy Pelosi was the bogie man for the congressional elections in 2010. Every Republican was running against her. She on the other hand, was running only in her district of San Francisco. People voted out their incumbent Democrats because the Republicans ran against Nancy, Harry Reid, and President Obama. Even Democrats who voted against the ACA were in trouble, not because of anything they had done, but because of the actions of others.

We do the same thing. We point to Boehner as the speaker, and say we must defeat him. He's a congressman from one small district in Ohio. If we're polled, we give Congress low marks, because we don't like this one, or that one, or whatever. But we are satisfied with our own congress human.

The same is true of the Senate. Look at the elections going on now. How many states are in play because the Incumbent did this, or that? Even Kentucky seems ready to re-elect McConnell. How can they do that when he has such poor favorabilities? How can they do that when he has said so many terrible things and obstructed so much? I thought Congress was unpopular. http://www.realclearpolitics.com/epolls/2014/senate/ky/kentucky_senate_mcconnell_vs_grimes-3485.html

All a congressman has to do is make their own little district happy. They can shit on the rest of the districts, and still win re-election if they are making a majority of the voters in their district happy.

I think, and I've thought this for a long time. The Senate is in jeopardy. I thought we would have to bust our asses to maintain the majority. Now, I think it's fairly short of certain, we're going to lose the majority. We have no one to blame but ourselves. But we won't do that, we'll blame the Rethugs, the idiot voters, the complicit media, and the Great Pumpkin. But in the end, it's us.

When voters don't get out and vote. When democrats get out and vote, democrats win, when they don't vote republicans win.

if the challenger is trailing but within striking distance, the race narrows at the end as last minute voters take the challenger seriously.

if the challenger is trailing by a wide enough margin so that a win no longer seems credible, then voters jump ship.


the mirror image might hold as well where the incumbent is trailing, albeit with a slightly different thought process.

Non-competitive races fluctuate wildly... because the people who show up are less reflective of the overall electorate.

But if an incumbent is at or below 50% (assuming a 2-way race), then that isn't the case.