The Hill engaged Democratic pollster Mark Penn to take a look at a dozen key House races where incumbents owed their seats to Barack Obama’s 2008 coattails, and not surprisingly, found Republican challengers leading in all but one of them.  In most of the cases, the leads were narrow enough that the races are still in play, and in none of them did the challenger get to the magic 50% mark.  Republicans have the edge and the momentum, but still have to make the final sale, Penn warns:

In a poll of 12 hotly contested races that could decide who controls the House in the 112th Congress, Republican challengers are beating freshman Democrats in 11 — and in the last one, the race is tied.

But The Hill/America’s Natural Gas Alliance (ANGA) poll also detected a glimmer of light for Democrats; not one of the 12 Republican challengers has reached 50 percent, and half of them have leads so small that they are within the margin of error.

The 12 districts this week are the first of 42 in The Hill/ANGA polls that will be conducted in the next four weeks. The first week’s focus is on freshmen, next week’s is on open seats, the following week’s is on two-term incumbents, and finally, in the week before the election, the polls will be in districts of long-term incumbents thought to be in trouble.

“This is a particularly volatile set of districts,” said pollster Mark Penn. “Overall, we see a strong Republican trend in these districts, but given where these numbers are, the races haven’t broken yet.”

The one race that is tied is Michigan’s 7th CD, where Tim Walberg vies to get his seat back from Mark Schauer, the current Democratic incumbent.  The two are locked up at 41/41 in a district that went for Obama by 10 points, but where Obama now gets a 46/50 approval rating.  Democrats have a one-point advantage in the sample for this poll, while Cook rates it at an R+2, which is close but perhaps giving too much of an edge for the Democrats.  Walberg narrowly carries independents 37/35, however, with plenty of room for improvement in a group that disapproves a little more strongly of Obama than the general population (45/52).

Otherwise, from the aggregate poll data, it’s easy to see why the GOP has taken leads in the polling.  Obama gets a dismal 42/55 in job approval across all of these districts and does even worse with independents, 40/56. In fact, when asked which Democrat they liked better in a presidential primary for 2012, Hillary Clinton won 37/31; among Democrats, Obama won, but just with 61% of the vote against 28% for Hillary, hardly a vote of enthusiastic support.

In these key swing Democratic districts, repealing ObamaCare is wildly popular at 56/32 — with 23% of all Democrats supporting repeal.  That’s probably why only 68% of Democrats say they are “passionate” about voting in four weeks, while 83% of Republicans feel that passion.  In very bad news for Democrats in these districts, only 56% of those 36 years of age and younger feel passionate, while 69% of the 37-54YO voters feel passionate — and 78% of the 55+ voters.  Republicans lead the generic ballot in all three age groups and overall at 45/39, but their biggest lead comes from middle-aged voters, 48/37.

And just in case Democrats want to tell people that this isn’t a referendum on the President, 69% of respondents said their feelings about Obama were an important or very important determining factor in their Congressional vote.  Among Democrats, it’s 74%, and Republicans 70%, with independents at 64%.  Those are referendum numbers, and given Obama’s unpopularity, bad news for Democrats nationwide.  I do find it interesting that Penn asked about almost no other issues than ObamaCare — nothing, say, on the economy or jobs, which are shaping up as two of the top issues in this midterm cycle.

It seems as though the GOP has a good chance at a clean sweep of these races, but it’s not over yet and no one has won anything until the polls close.