A Public Policy Polling survey of Delaware’s Republican Senate primary released Sunday night showed Rep. Mike Castle and tea party favorite Christine O’Donnell statistically tied, a strong indication that Tuesday’s contest is likely to go down to the wire.

O’Donnell led Castle 47 percent to 44 percent in what is likely to be the last poll before the primary. PPP, a Democratic polling firm, surveyed 668 likely primary voters on Saturday and Sunday. The poll had a margin of error of 3.8 points.

The poll found that Castle’s popularity took a dramatic hit over August, as the race began to draw more attention. In a similar PPP poll taken in August, Castle’s favorable/unfavorable rating was 60 percent/25 percent. But in the new survey, 43 percent said they viewed the longtime Congressman and former governor favorably and 47 percent said they viewed him unfavorably. The net negative rating can be attributed to 55 percent of voters’ belief that Castle is too liberal, the pollster explained in a memo.

Castle had been considered the de facto GOP nominee and frontrunner in the November contest until tea party support for O’Donnell surged in the past few weeks and the race began garnering national attention.

It’s somewhat of an understatement to say that national Republicans have a lot riding on having Castle become the party’s nominee. If O’Donnell wins the primary, it’s hard to see how Republicans will compete at all this fall in the Democratic-leaning state. The pollster observed that the closeness of the GOP race will benefit likely Democratic nominee Chris Coons regardless.

“The biggest winner of the Delaware GOP primary may end up being Chris Coons,” PPP President Dean Debnam wrote in the memo. “Running against O’Donnell or a wounded Castle will put him in his strongest position since he entered the race.”

The PPP poll also questioned respondents about the Republican primary in the race to succeed Castle in the House. It found real estate developer Glen Urquhart ahead of lawyer Michele Rollins, 50 percent to 39 percent. Rollins has widely been viewed as the frontrunner to win the nomination. But Democrats are favored to pick up the seat in November.