Columbus -- Republican U.S. Sen. Rob Portman continues to widen his lead against Democratic challenger Ted Strickland among voters surveyed by the Quinnipiac University Polling Institute.

In a poll released Sept. 9, Portman was ahead of the former Ohio governor, 51 percent-40 percent -- that's up from 49 percent-40 percent a month ago and 47 percent-40 percent in July.

Portman and Strickland were essentially tied in several earlier polls, though Strickland was ahead, 48 percent-39 percent, in Quinnipiac's early polling of the race in April 2015.

Portman also continued to fare better than Republican senators in other swing states, though the GOP incumbents in Florida and North Carolina were outpacing their Democratic opponents.

"Sen. Portman has taken a double-digit lead in Ohio where the once tight race seems to be moving away from Democrat Ted Strickland, a former governor who showed strength early but whose chances have faded recently," Peter A. Brown, assistant director of the Quinnipiac Poll, said in a released statement. "And with this large deficit, Strickland may find it difficult to raise money."

The Connecticut-based polling institute regularly gauges the opinions of voters in Ohio and other swing states on candidates and issues. Its latest Senate race survey, conducted over the past week, included 775 likely Ohio voters. The results had a margin of error of 3.5 percentage points.

Portman's campaign spokeswoman touted the senator's growing lead.

"Even Democrats are abandoning Ted Strickland as momentum grows behind our campaign as we highlight the results Rob is delivering for Ohio families and as we've gained multiple union endorsements and contacted over 3.5 million voters through our unprecedented door-to-door and phone programs," Michawn Rich said in a released statement.

Speaking after a press conference in front of the governor's residence near downtown Columbus Sept. 9, Strickland remained confident in his campaign.

He said a Quinnipiac Poll during his unsuccessful reelection campaign against John Kasich had him down by a larger margin, but he lost that race by a couple of percentage points.

"I think that's relevant information," Strickland said. "/ If they have me down by 11, that means I'm going to win by 3-4, if we use past history as an example of what could possibly happen in this election."

He added, "I'm a little behind because I've been subjected to the most outrageous expenditure of attack ads in the history, I believe, of the U.S. Senate, and yet I am still in this race/ We are just at the official beginning of the campaign, so I am feeling pretty good."

Marc Kovac is the Dix Capital Bureau Chief. Email him at or on Twitter at OhioCapitalBlog.