As coverage of the crowded and unsettled 2008 Presidential race has accelerated in recent months, one recurring story line has focused not on the 19 candidates already in the race—but on a few people still on the sidelines.

With surveys indicating that Republicans are less satisfied with their party’s presidential hopefuls than Democrats, a good deal of this coverage has focused on former GOP House Speaker Newt Gingrich and former Republican Senator Fred Thompson, with the latter expected to enter the race soon. On the Democratic side, there’s been occasional coverage speculating on a possible bid by former Vice President Al Gore.

But New York Mayor Michael Bloomberg’s June 19 announcement that he was dropping his Republican affiliation triggered a frenzy of speculation that is unusual even in this media-saturated campaign season. Although Bloomberg has downplayed any desire to seek the White House, the prospect of the largely non-ideological billionaire running as an independent candidate jolted the political Richter scale.

The 2008 presidential contest was the leading story last week, filing 11% of the newshole in the period from June 17-22, according to PEJ’s News Coverage Index. (It was the top event in the cable (18%) and radio (12%) sectors last week.) And about 45% of all the campaign stories PEJ examined involved Bloomberg.

It seemed like everybody was talking about New York’s mayor. He and California Governor Arnold Schwarzenegger were the smiling cover boys on the June 25 issue of Time magazine. Writing in the June 24 Washington Post, Ed Rollins, who helped direct Ross Perot’s 1992 third-party candidacy, basically embraced the idea of a Bloomberg run in a column headlined, “Come on In, Mike. It Could Be a Wild Ride.”

“Here at home, a political bombshell tonight,” was how CBS anchor Russ Mitchell broke the news of Bloomberg’s party change on the June 19 newscast. “There has been speculation Bloomberg might run for president as an independent.”

“Can a brilliant—and he is—successful—and he is—competent—he’s proven to be—Jewish executive be elected President of the United States?” That’s the question liberal radio talk host Ed Schultz asked his listeners on June 20.

That same day Bloomberg’s hometown paper, The New York Times, ran this page-one headline that was sober without foreclosing any options: “Bloomberg Cuts Ties to G.O.P., Fueling Further Talk of ’08 Bid: Mayor Faults Both Parties as Timid on Big Issues.”

While the Bloomberg boomlet fueled coverage of the White House race, violence and tensions in the Middle East also generated major attention last week. The major U.S. offensive, “Operation Arrowhead Ripper,” against Iraq insurgents helped make events in that country the second-biggest story of the week (9%). The situation on the ground in Iraq was the top story in the newspaper (10%), online (15%) and network TV (12%) sectors.

Given the continuing fallout from the Palestinian fighting that effectively gave Hamas control of the Gaza Strip and left Fatah in charge of the West Bank, the Palestinian crisis was next at 7%.

Two breaking-news tragedies also made the top-10 story list. The disappearance of pregnant Ohio woman Jessie Davis (her body was subsequently found and her boyfriend charged with her murder), was the fourth-biggest story at 5%. And the June 18 furniture store blaze that claimed nine firefighters in Charleston, South Carolina was the number six story at 3%.

Immigration was the fifth-biggest story (4%) with the fate of the controversial immigration bill hanging in the balance. While coverage is likely to spike if there is a final legislative showdown this week, the story cooled a bit last week after being the top subject from June 10-15.

PEJ’s News Coverage Index is a study of the news agenda of 48 different outlets from five sectors of the media. (See a List of Outlets.) It is designed to provide news consumers, journalists and researchers with hard data about what stories and topics the media are covering, the trajectories of major stories and differences among news platforms. (See Our Methodology.)

News about the Iraq war last week also confirmed a recent pattern in the coverage. Given the significant U.S. military offensive and the announcement that 14 U.S. troops had died in a two-day period, events in Iraq constituted the second-biggest story. With a number of stories focused on care given to wounded veterans returning from Iraq or Afghanistan, the impact of the war at home was also a top-10 story last week (eighth at 2%).

At the same time, the Iraq policy debate—the Washington-based battle over war strategy—generated only 1% of last week’s coverage and failed to make the top-10 story list. Those findings are indicative of a trend in recent weeks in which coverage of the political debate over the war has diminished substantially.

For the first three months of this year, PEJ found that the policy debate was the leading news subject by a large margin, accounting for 12% of all the coverage. (The next biggest story was the 2008 campaign at 7%.) But on May 24, after a lengthy political showdown, Congress approved war funding without including troop withdrawal timetables. Since then—in the period from May 27-June 22—the policy debate has been the sixth-biggest story attracting 3% of the coverage. This suggests that the May 24 vote was viewed as a major victory for President Bush over the Democratic-led Congress that, temporarily, brought some kind of resolution to the policy fight.

There is reason to believe the subject will heat up again in September (if not sooner), when General David Petraeus is slated to deliver his much-anticipated progress report on the U.S. troop surge.

For the second week in a row, Palestinian conflict was a top-five story as the action moved from the battlefield to the diplomatic arena as the U.S. and its allies tried to bolster the new Fatah-based government of Palestinian President Mahmoud Abbas.

President Bush and Israeli Prime Minister Ehud Olmert met in Washington last week to discuss the new situation in the Palestinian territories. And a June 21 NPR “Morning Edition Report” that speculated on the likelihood of an Israeli military assault against the Hamas-controlled Gaza Strip reported that “the Israeli government is trying to figure out how to deal with the newly divided Palestinian population.”

Yet for all the concern about the Middle East, the U.S. presidential race generated the most media attention for the second time in three weeks. And if speculation about Michael Bloomberg joining the fray fueled much of that coverage, it was a pretty good week for another possible entry as well.

“He’s not even officially running yet, but Republican Fred Thompson is certainly shaking up the race for his party’s presidential nomination,” declared Fox News Channel daytime anchor Jane Skinner on June 19.

The good news for the ex-Senator and “Law & Order” star? A new Rasmussen Reports poll among likely Republican primary voters revealed that Thompson, while still not officially a candidate, is now leading the GOP field, topping previous frontrunner Rudy Giuliani by a razor slim 28% to 27% tally.

“What it really is telling us,” said pollster Scott Rasmussen, “is the rest of the field hasn’t caught fire.”

Mark Jurkowitz of PEJ