Support for Sen. Marco RubioMarco RubioThe Hill’s 12:30 Report Trump at immigration crossroads Poll: Majority of GOP voters wish they chose another presidential nominee MORE's (R-Fla.) potential presidential bid has slipped and Sen. Rand PaulRand PaulTrump, Clinton boost Snapchat spending Clinton enjoying edge over Trump in Silicon Valley Trump gets little backing from Silicon Valley MORE (R-Ky.) leads in the key early-voting state of Iowa, according to a new GOP primary poll conducted by the Democratic firm Public Policy Polling.
Paul, meanwhile, has risen from 10 percent support in February to 18 percent today.
The Florida senator's dip could be driven more by others' rise than his own stature, however.
Rubio's favorable rating stayed unchanged at 54 percent, with a statistically insignificant change from 13 to 14 percent in those who view him unfavorably.
The possible candidates are all very close to one another, however, well within the poll's 6.2 percent margin of error.
Paul is just 2 percentage points ahead of New Jersey Gov. Chris Christie (R), who has 16 percent support.
Former Florida Gov. Jeb Bush (R) pulls 14 percent, Sen. Ted CruzTed CruzTrump at immigration crossroads Poll: Majority of GOP voters wish they chose another presidential nominee Trump attacking immigration issue openly and honestly MORE (R-Texas) is nipping at Rubio's heels at 10 percent support and former Sen. Rick Santorum (R-Pa.), who won Iowa's 2012 presidential caucuses, sits at 6 percent.
This isn't the only recent PPP poll showing Rubio trailing the field of potential candidates, after some polls earlier this year showed him as the front-runner.
PPP's recent poll of Texas Republicans found Rubio in sixth place among candidates, with 6 percent support, and a recent poll of Montana Republicans found him in fifth place.
On the Democratic side, Hillary ClintonHillary Rodham ClintonQuestions posed to Clinton for sworn-oath responses in email case Poll: Clinton leads by 5, with both candidates increasingly unpopular Poll: Clinton up 8 over Trump in Pa. MORE dominates her potential primary opponents, with 71 percent support to 12 percent for Vice President Biden and 5 percent for Sen. Elizabeth WarrenElizabeth WarrenWarren leads 20 senators in letter grilling EpiPen maker No, Tim Kaine is not the most liberal member of Congress Voters deserve to know what candidates think of the Fed MORE (D-Mass.). In the general election, Clinton leads all comers by 7 percentage points or more.
PPP's automated poll of 668 voters, including 250 GOP primary voters and 260 Democratic primary voters, was conducted from July 5-7.
The margin of error for the total poll was 3.8 percent, with margins of error of 6.1 percent and 6.2 percent for the Democratic and Republican primary samples.