is there often a warning sign before someone loses re-election?

[hopper]

In the workplace, it is often said that there are several warning signs before being fired. Is the same true in congress? I would say the main issue is declining percentages if one's percentages gradually start declining, then it means that the next wave against your party or even a neutral year, you're toast.

For a lot of the unseated incumbents this year, many of were only in their first or second term and had never won by an extraordinary margin so it wasn't much of a surprise. For the older members, a lot of them were out of nowhere and some of them weren't that unexpected:

Chet Edwards had only gotten above 60 percent of the vote three times in his career (1992, 1996 and 1998) and his luck was about to run out sooner of later

Kanjorski ran six points behind Obama in 2008 so it wasn't surprising to see him lose.

A few others were more unexpected
Boucher had never had a tough re-election race since the 80s and had run unopposed previously so there was no warning sign

Ike Skelton had always won above 65 percent and the only close race he had was in 82 when his district was merged with a republican congressman. His percentages hadn't been declining so it was probably a shock that he lost.

Boucher-his district was getting more Republican though. 2004 PVI: R+7 2008 PVI: R+11. I think he voted for Cap & Trade too and his district did not like that. A district like that just screams conservative in that its a Virginia district in the western part of the state by the Tennesee border I believe. So basically there was alot of factors at play when Boucher got defeated.

Skelton: I think his district was Republican to start with and he had a good opponent when he lost to Vicky Hartzler.

[hopper]

Close races and barely scraping by:


I think Conrad Burns(R) went through this scenario while US Senator of Montana. He had a few close races and finally his luck ran out.

I think former rep. Gary Franks(R) of Connecticut the same scenario happened. He won 3 way races in 1990 and 1992 and beat James Maloney in 1994 I think and his luck ran out in 1996 and he lost in a re-match to Maloney. His district was conservative back in the day to what you think of it nowadays. The district has moved left of center. Of course the 5th district does include the old 6th district too which it didn't back in the 1990's/early 2000's.

[hopper]

I think former rep. Gary Franks(R) of Connecticut the same scenario happened. He won 3 way races in 1990 and 1992 and beat James Maloney in 1994 I think and his luck ran out in 1996 and he lost in a re-match to Maloney. His district was conservative back in the day to what you think of it nowadays. The district has moved left of center. Of course the 5th district does include the old 6th district too which it didn't back in the 1990's/early 2000's.

Speaking of Connecticut, Sam Gejdenson (D-CT-02) won by only 21 votes in 1994 (and had had what Wikipedia describes as very close races in 1982 and 1992 (against the same opponent as in 1994 I know) as well) before losing in 2000.

Yeah Munster must have been a very good opponent though because Gejdenson won in 1996 and 1998.  Of course the 1994 Republican Wave did have something to do with that race being close in the first place but not that close(21 votes!)