Iowa Gov. Chet Culver's (D) re-election prospects are growing dimmer to the point where you'll hear whispers about another retirement. The Des Moines Register's Iowa Poll shows that Culver's approval rating is down to 36 percent, with 53 percent now disapproving of his job performance. That's down from 40 percent approval in November and 50 percent approval in September.

Last January, Culver's approval rating was at his all-time high: 60 percent. Now, he's at a low point unseen by his three predecessors. That's especially bad news given that he could face one of them -- former Gov. Terry Branstad (R), this fall:

General Election Matchups (531 LVs, 1/31-2/3, MoE +/- 4.3%)
Branstad (R) 53 -- Culver (D) 33 -- Und 9
Vander Plaats (R) 43 -- Culver (D) 40 - Und 12
Culver (D) 41 -- Rants (R) 37 -- Und 14
Culver (D) 41 -- Roberts (R) 36 -- Und 15

Culver isn't the most vulnerable Democratic incumbent -- that designation still belongs to New York's David Paterson. But unlike Paterson Culver was elected to the post in his own right. Colorado's Bill Ritter (D), with somewhat better numbers, abandoned his re-election bid last month. On the Republican side, Nevada's Jim Gibbons is the incumbent least likely to be re-elected; he's likely to lose in the primary.

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