Pollster.com's methodology of putting all polls into a regression line was vindicated by the 2008 elections, so these findings cannot be dismissed. Both Democratic (by about 3%) and Republican (by about 4%) self-identification have increased over the past five weeks. Independents have declined by 7-8%. This means that we are going through a period in our national political discourse where people are taking sides, not moving toward an undifferentiated center.
This shift coincides with the tea-parties, the torture debate, Specter's party switch, and the abortion debate. All in all, you have to hand it to wingnuts: even when they are out of power, right-wingers are still driving the debate, and still good at making people take sides. Even the Specter switch led most to discuss the implications it held for the Republican Party, rather than for Democrats or progressives.
What Republicans appear to be doing right now is shoring up their base with these arguments. They are bringing their anti-government, anti-choice, harsh foreign policy voters back into the fold. It has allowed them to make up some ground on Democrats, though they still trail by a sizable 8%. It seems unlikely to me that this is a path back to competitiveness for Republicans in and of itself. Even with all of their best recruits, they are likely to lose more Senate seats in 2010. However, a more coherent base, combined with an economy that is still struggling in 2012, might be enough to make for a close election in 3.5 years time. (That is, it will be competetive, unless either Romney or Gingrich is the nominee. Those two will never become President).