NEW YORK -- During the past several months of the Republican primary campaign, presumptive GOP nominee Mitt Romney received a mix of positive and negative coverage, while President Barack Obama got "consistently negative" coverage, according to a new study from Pew's Project for Excellence in Journalism.

The PEJ study, which examined coverage from the period between Jan 2 and April 15, found that "Obama's negative coverage exceeded positive coverage in 14 of 15 weeks studied, while positive coverage outweighed negative coverage for Romney in six of the 15 weeks and was fairly evenly divided in four more."

While former House Speaker Newt Gingrich often railed against the "elite media" and former Sen. Rick Santorum famously called out a New York Times reporter, Romney, the former Massachusetts governor, generally steered clear of media bashing. But as he pivots to the general election, Romney has begun taking jabs likely to play well with the Republican faithful.

On April 15, Romney told attendees at a closed-door fundraiser held in Palm Beach that most TV commentators "tend to be liberal." Two days later, Romney said in a Breitbart.com interview that "many in the media are inclined to do the president's bidding and I know that's an uphill battle we fight with the media generally." He also spoke of a "vast left wing conspiracy" against him.

In addition, the Romney campaign announced Thursday it had hired as its national security spokesman Richard Grenell, a former Bush administration official who sparred with reporters at the United Nations, perhaps signaling that it plans to take a harder line with reporters during the general election. Since leaving government, Grenell has become a vocal media critic on Twitter and on his recently removed personal website.

Given Romney's recent swipes at the press, the Obama campaign was quick to seize on PEJ's findings.

"With all of this fawning coverage for Mitt Romney and the Republicans, sounds like the vast left wing conspiracy Romney invented better start staffing up," Obama campaign spokesman Ben LaBolt said in an email to The Huffington Post.

PEJ found that Romney's media coverage "became measurably more favorable and the portrayal of his rivals—particularly Rick Santorum—began to become more negative and to shrink in volume" after Romney narrowly won the Michigan primary by three points on Feb. 28. At that point, according to PEJ, the media narrative of Romney as inevitable nominee was essentially set and coverage took a "dramatic turn for the better and stayed that way until he had a virtual lock on the nomination."

A Romney spokesman did not immediately respond to a request for comment on the study and expectations about media coverage going forward.

But PEJ director Tom Rosenstiel told The Huffington Post he expects coverage to even out as Obama faces a single Republican candidate and no longer has to field criticism from a pack of multiple primary contenders.

"Now this gunfight is one-on-one," Rosenstiel said. "The Romney campaign and the Obama campaign will be facing off and I think it's likely you'll begin to see the coverage of the two match up, at least to the extent that the press is conveying the criticism on each side."

During the primary, Romney's rivals either didn't get as positive coverage as he did or found themselves fall off the media's radar as Romney took a sizeable delegate lead.

In the 15 weeks studied, PEJ found that Santorum –- Romney's closest rival before he pulled out of the race two weeks ago -- "never enjoyed a sustained period of positive press." (Before the Iowa caucus, Santorum had received less media coverage than any other Republican candidate.)

Meanwhile, Gingrich only received more positive coverage than negative during the week he won the South Carolina primary. However, three weeks after his big win, Gingrich "registered in less than 1% of the campaign stories," according to the study. And while Rep. Ron Paul (R-Texas) received the "most consistently positive portrayal of any candidate in the race," press coverage overall was scarce.

In producing the study, PEJ relied on computer-assisted analysis of over 11,000 news outlets, along with human coding of 52 top news outlets across print, online broadcast, cable, and radio.

As the media turns its attention to the general election, there will likely be increased focus on how Romney deals with press. His recent bout of media criticism became a topic conversation Sunday on CNN's "Reliable Sources."

WATCH BELOW: