There is an interesting article in The Economist this week, which states  "The Conservatives are doing well, but not well enough." That's probably a fair assessment.
The point is that despite the government's recent woes, and the sustained poll lead they have produced for Cameron's opposition, the Tories have not managed to really pull away from Labour. As The Economist notes, in 1995 Labour were scoring 60 percent, more than 30 percent ahead of the Tories. By contrast, Cameron's Conservatives are only averaging  a ten-point lead, with 41 percent to Labour's 31. Of course, that is their best lead since 1992 and it represents a truly remarkable turn around from just a few months ago. But thanks to the structural unfairness of the British electoral system (the Conservatives need many more votes than Labour to win the same number of parliamentary seats) it is not yet enough to be sure of victory.
The main question for the Tories is, what can they do to propel themselves further ahead? The Economist points to two issues. The first is personnel - the shadow cabinet as a whole needs to perform better. Too many of them are completely unknown to the wider public, and do not seem to be particularly proactive. This is foolish: the Conservatives cannot simply hope for the government to lose the next election, they will have to work tirelessly to win it.
The second issue is policy. The problem is not, as is often suggested, that there isn't enough of it, or that it isn't detailed or radical enough. In fact, Cameron's policy commissions have provided him with a wealth of promising ideas, particularly on education and welfare reform (which may prove to be the most important challenges facing the next government). But what the Conservatives have not yet developed is an overarching theme or narrative that holds everything together and makes people understand just what a Tory government will be all about.
Ultimately, people vote for a vision, not for a handful of good policies. The challenge that remains for the Conservatives is making their vision the most attractive one on the market.