Among voters in the key primary state Iowa, U.S. Sen. Rand Paul is the strongest Republican in the field of prospective 2016  presidential candidates,  says a new poll by Quinnipiac University.

Kentucky’s junior senator leads current Vice President Joe Biden by five points among Iowa voters— and he trails former Secretary of State Hillary Clinton, the presumed Democratic frontrunner, by only four points.

Those totals are better than Sen. Marco Rubio, the Floridian who is also a leading Republican contender for the 2016 presidential election.

In the Quinnipiac poll, Rubio barely edges Biden and trails Clinton by nine points. 

The polling numbers come on heels of his keynote speech to Iowa Republicans weeks ago. But a major reason for Paul’s strong standing in Iowa is his perception among Iowa’s independent voters.

“In general Sen. Paul appears to be the better GOP candidate at this point in Iowa,” said Peter A. Brown,  assistant director of the Quinnipiac University Polling Institute, in a polling memo.  ”Part 
of the reason may be the publicity from his recent high-profile visit to the state, but more likely 
is that he begins with a solid base of support—the folks who voted for his father in the 2008 and 
2012 caucuses.”

Paul has consistently moved up the pecking order in the potential GOP presidential field—in both early national and state polling.

In early April, a poll by Public Policy Polling showed Paul was second leading Republican nationwide in the GOP field, trailing only Rubio. A poll by Quinnipiac at the same time showed Paul in third nationally. 

Later that month, PPP released a poll showing Paul was leading all potential GOP candidates  in New Hampshire, another key early presidential state. 

Paul recently headlined the Iowa Republican Party’s annual dinner and co-headlined a similar dinner in New Hampshire with Republican National Committee chairman Reince Priebus.