Without anything as significant symbolically as Labour's pro-nationalisation Clause Four to scrap, Mr Cameron has chosen to move on multiple fronts.

ECONOMIST: Bagehot

Health and education, says the Tory leadership, are their clause four.

ECONOMIST: Why the Tories are defending the welfare state

MEPs signed a defence of the old Clause Four, which used to pledge the party to nationalisation before it was abolished at the instigation of Mr Blair.

ECONOMIST: Britain and Europe

Some of Mr Hague's lieutenants compare their leader's move with Tony Blair's decisive call on Labour in 1994 to delete the hallowed Clause Four from the party's manifesto.

ECONOMIST: Roll up that map of Europe

Mr Davies announced his party had arrived at a "clause four moment" (echoing Tony Blair's modernisation of Labour), warning that some were still fighting the devolution battles of the 1990s.

BBC: Sergeant Wilson, Corporal Jones and the prime minister

He agreed with the four conservatives that the law violated the Commerce Clause of the Constitution, which was the main claim of the 26 states that sued.

WSJ: Toodle-oo to 2012

There are four important modern decisions about the limits of the Commerce Clause.

FORBES: Middle District of Pennsylvania Rules Three Obamacare Provisions Unconstitutional

In the Seattle case, the Court ruled by a five-to-four vote that the integration plan did indeed violate the equal-protection clause of the Constitution, and Roberts assigned himself the opinion.

NEWYORKER: No More Mr. Nice Guy

The Eleventh Circuit discussed four cases that either limited or did not limit Congressional power under the commerce clause.

FORBES: Obamacare Insurance Mandate - Another Circuit Heard From

In it, the professors say the agreement among 46 states (four others signed their own pacts with the tobacco industry) violates the Compact Clause of the U.S. Constitution banning treaties between states.

FORBES: Odd Couple Files Brief Against Tobacco Settlement