Paul Ryan claimed in his convention speech that President Obama promised to keep open the auto factory in his home town, which then subsequently closed. Liberal commentators jumped on that, claiming that in fact the factory closed under the Bush administration. Sounds like good fact checking, EXCEPT that apparently the fact checkers need fact checking themselves. See the posting Ryan's Fact-Challenged Fact Checkers for more fact checking on the fact checkers. Actually, it's a bit hard to see how Obama could have been giving his speech at the factory if it was already closed, so one might have been suspicious of the commentator's "fact checking" right from the start..
I'm not inclined to take very seriously any of the negative advertising, from either party, going on right now - it is so obviously partisan that it is essentially meaningless.
Right now one thing matters above all - getting the nation's fiscal house back in order, which means only three things in the short term (1) stimulating more private business activity, (2) eliminating the federal deficit and beginning to reduce the debt load, and (3) reforming the entitlement programs, primarily Medicare and Medicaid, that are currently unsustainable. In the medium term one might add two more related items: (4) improving our failing education system, and (5) upgrading the nation's infrastructure. All I care about right now is what each party will do for these items.
We already know what the current administration will do, based on what they have done for these items over the last four years -- almost nothing effective.
Will Republicans do any better? It's hard to know.