The Conservatives haven't "won the economic argument".
All they have done is repeated "Labour can't be trusted on the economy" over and over again.
Their basic argument on the economy is:
- there was a recession in 2008/09, Labour were in charge so this is Labour's fault
- the economy took ages to recover between 2010 and 2013, but this is because we had to make tough decisions because of Labour's fault
- we are cutting spending because we have to make tough decisions because of Labour's fault
Now this argument is fine, until you reach the point where you say "Labour are now an irrelevance and this is Tory Britain", which the Conservatives are moving closer towards.
The next time there is a crash in the banking system or a recession due to global factors which are outside the Conservative government's control, which could easily happen in the next 5 years, the Conservatives have a problem, how do they argue it away? A recession would drive up the deficit and drive up unemployment so how do they argue against that?
They can't blame the bankers because those are key Conservative allies.
They can't say the recession was due to too much government spending, because then people will ask why did they spend so much.
They can't say the recession was due to Blair/Brown because they haven't been in power for ages.
This is the point where the Conservatives will start to struggle with their claim that they have "won the economic argument".
John Major came unstuck when the UK fell out of the Exchange Rate Mechanism in 1992, because even though Labour had supported ERM entry for a long time (longer than the Conservatives), it was ultimately the Conservative government that took the UK in to the ERM, and it was under the Conservatives that we crashed out at the cost of many billions and a lot of international credibility. They couldn't pin that on Labour. In the 1997 election campaign the Tories were trying to bring up the 1970s and talk about that as an argument against Labour but the electorate weren't listening, the buck stopped with the Tories and they wanted their pound of flesh from the Tories.
So the Conservatives need to be careful with their hubris. I've seen a lot of triumphalism recently, Labour is finished, Labour is an irrelevance, the Conservatives are the natural party of government. Once you take that line you have to accept accountability because the electorate are going to put every grievance at the Conservatives' door. Also if you pin the 2008/09 financial crisis on the Labour government rather than "global forces" then you can't claim that a subsequent recession was actually not due to a Conservative government but due to "global forces" as you have set the electorate up to blame the incumbent government.