A new poll throws some water on the idea that Rep. Mike Castle (R-Del.) hurt his Senate prospects with his vote against the health care bill.

While Susquehanna showed Castle dropping behind Beau Biden (D) by five points after the vote, Public Policy Polling (PPP) today shows Castle holding steady with a 45-39 lead.

What’s more, while Susquehanna speculated about the health care vote hurting Castle, the Democratic-leaning firm PPP actually tested the question. Turns out, more Delaware voters say they are opposed to the health care plan (46 percent) than support it (43 percent).

The poll, combined with Delaware Gov. Jack Markell’s (D) comments this week, will give the GOP plenty of ammo to suggest that health care isn’t even a winner in a 62 percent Obama state.

Castle remains popular among independents, carrying a 52-23 lead with that group, and he also takes 20 percent of Democrats.

Obama remains over 50 percent in the state, but he is down to 53 percent after polling in the 60s earlier this year. Nearly one-fifth of those who said they voted for Obama (18 percent) said they will back Castle in the Senate race.

Castle’s favorability-unfavorability numbers (55-28) are also a good deal better than Biden’s (43-35).

“Mike Castle has more appeal to Democrats and independents than any other Republican Senate candidate in the country, and that’s allowing him to hold the early lead in this race,” PPP President Dean Debnam said.

It’s going to be very hard for any other Democrat to beat Castle, but Biden is taking his time in deciding on the race. There’s been a lot of talk in recent days about Democrats retiring and dropping out of certain races, but if Biden opts not to run, that might be the biggest sign of trouble ahead for Democrats.