Five weeks and an official announcement of her candidacy later, Hillary Clinton has increased her early advantage over John Edwards in a new poll of likely Democratic Iowa Caucus voters by American Research Group.

Clinton, who declared her run for the presidency approximately one week before the poll’s field dates, expanded her 11-point 31-20 lead over Edwards to 17 points (35-18) in the new February poll. Barak Obama’s support also increased from 10 to 14 percent. Homegrown former Iowa Governor Tom Vilsack continues to languish behind these favorites—with his support declining from 17 to 12 percent. A recent Iowa Poll by the Des Moines Register found more Iowans do not want Vilsack to run for president (47 percent) than do (40 percent).

On the Republican side, likely GOP Caucus voters still give Rudy Giuliani the nod (27 percent) even though the former federal prosecutor and New York City mayor has not yet officially entered the race. The only positive movement in the new February poll was towards former Massachusetts Governor Mitt Romney—whose support increased from 6 to 11 percent.

As a reminder of the volatility in the Iowa Caucuses, consider this: these Iowa polls are nearly 12 months out from Caucus Day. In polls by American Research Group ending just four days before the Caucuses in 2004, John Kerry polled at 21 percent and John Edwards polled at 22 percent. Kerry ended up with 38 percent of the Caucus vote and Edwards with 32 percent in a huge 11th hour shift in momentum towards those candidates—and away from Dick Gephardt and Howard Dean.