Charlie Cook, a highly respected and non-partisan political analyst, has moved two more Pennsylvania Congressional seats from the Democrats' "Safe Column" to "Likely D" -- an indication of how difficult 2010 will be for incumbent Democrats thanks to the missteps of Barack Obama, Nancy Pelosi and Harry Reid.

The latest incumbent Democrats on shaky ground are Patrick Murphy and Tim Holden. That brings the total number of Pennsylvania Congressional Democrats who are vulnerable in 2010 to 7, according to The Cook Political Report:

PA-3 Kathy Dahlkemper
PA-4 Jason Altmire
PA-8 Patrick Murphy
PA-10 Chris Carney
PA-11 Paul Kanjorski
PA-12 John Murtha
PA-17 Tim Holden

Republicans could retake a half-dozen Pennsylvania seats after poor showings in the 2006 and 2008 election cycles.

Key excerpts from The Cook Political Report:

PA-08 Patrick Murphy Solid D to Likely D

In bad years, parties find that tamping down problem districts is a lot like playing whack-a-mole. Democrats weren't counting on having to spend much time thinking about this seat in 2010, but former one-term GOP Rep. Mike Fitzpatrick's bid makes this district a new concern for Democrats. The 2006 race between Murphy and Fitzpatrick was one of the closest in the country: Iraq War veteran Murphy unseated Fitzpatrick by less than a percentage point in this suburban Bucks County district. Now, Republican leaders have succeeded in convincing Fitzpatrick, who is apparently healthy after a bout with cancer, to make a comeback…Murphy is a solid fundraiser with $624,000 in the bank, while Fitzpatrick must start from scratch. But the current state of affairs for Democrats in Pennsylvania means this rematch should only become more competitive.

PA-17 Tim Holden Solid D to Likely D

At the outset of the decade, Republican redistricting had caused some to leave Holden for dead. Instead, Holden has rather impressively made a happy home out of this GOP-leaning district…But now, GOP state Sen. Dave Argall, who shares Holden's Schuykill County base, is entering the race. Holden begins the race with a large reservoir of goodwill. In 2008, he took 64 percent of the vote while President Obama took just 48 percent here…But Holden has never had to run for reelection in this district in such a challenging environment.