[kergonath]

See my other reply upthread. I agree that this change was designed to ensure a majority for the president. But the political landscape has changed lot since then, in ways that were difficult to foresee. It is not unimaginable to end up with an unpopular president elected by default, even as their party gets ~30% of the seats at the parliament. Then, the opposition has strong incentive to hammer out a coalition government.

The 5th republic is founded on the premise of strong parties. In 2002, the landscape has been dominated by a right-wing coalition (UDR, RPR, UMP and their satellites) and a left-wing one (SFIO, then PS) for half a century. The candidate of both mainstream blocks polling below 15% was very hard to imagine.

Coupling both presidential and legislative elections might not be enough to avoid further splintering in the future.