The Des Moines Register poll shows Agriculture Secretary Tom VilsackThomas J. VilsackUSDA: Farm-to-school programs help schools serve healthier meals OVERNIGHT MONEY: House poised to pass debt-ceiling bill MORE (D) as the only candidate tested receiving majority support, with 56 percent of those polled saying they consider him an "appealing candidate" for senate, while only 35 percent say they don't.

Rep. Tom Latham (R-Iowa) also posts a higher percentage of Iowans expressing interest in his bid, with 40 percent saying they see him as an appealing candidate, while 34 percent say they do not.

However, only 36 percent of respondents view Braley as appealing, while 33 percent do not. A full 31 percent say they're still not sure about the only candidate officially in the race — the highest percentage of unsure voters of any candidate polled.

Braley announced his candidacy on Thursday, the same day the poll was released, and the numbers indicate he's got a long road ahead in introducing himself to voters.

But the four-term congressman has proven to be a tough campaigner. He narrowly held on to his slightly Democratic-leaning district during the 2010 GOP wave despite being a top target, and won by a wide margin in 2012 against a strong challenger.

No Republicans have announced bids for the seat yet, though both Reps. Steve King (R-Iowa) and Latham are considering running. The Des Moines Register poll indicates voters prefer Latham to King, as a plurality of those polled, 41 percent, say they don't see King as an appealing candidate, while only 33 percent said they were interested in his candidacy.

The poll was conducted from Feb. 3-6 among 802 Iowans, and has a margin of error of plus or minus 3.5 percentage points.