Scott Walker continues to lead the field of Republican presidential candidates in Iowa, according to a poll of likely Republican Iowa caucus participants released on Thursday.

The poll, commissioned by the Iowa Renewable Fuels Association, also found a 5-point drop in support for Sen. Rand Paul compared to a similar survey by the Des Moines Register late last month.

Walker received 19 percent in the poll, followed by Ben Carson at 13 percent and Jeb Bush at 11 percent. Marco Rubio received 9 percent, followed by Rick Perry at 7 percent, Ted Cruz at 6 percent and Rand Paul at 5 percent.

Paul has been sliding in Iowa caucus polls since January, when he was in second place behind Walker at 14 percent. The latest IRFA poll has Paul in 7th place, tied with "Unsure."

According to The Iowa Republican’s Craig Robinson, the timing indicates that the drop in support for Paul could be related to his recent comments on the Islamic State (IS, also known as ISIS or ISIL):

The IVR poll, produced similar results to the latest Iowa Poll conducted by the Des Moines Register, but it does show some movement in the middle of the pack. The biggest mover was Kentucky Senator Rand Paul who dropped five-points since the Register’s poll at the end of May. Paul’s drop may be a result of comments he made about Republicans being responsible for the creation of ISIS at the same time the poll was in the field.

The poll surveyed 1,235 likely Republican Iowa caucus participants between June 8 and June 10. It has a margin of error of plus or minus 2.8 percent.