Zimbabwean President Robert Mugabe's party, the Zimbabwe African National Union-Patriotic Front (ZANU-PF), has put the brakes on a constitutional referendum because the party is afraid it will lose the next election to the opposition party, the Movement for Democratic Change (MDC).

According to the South African news outlet Mail & Guardian, one particular clause in the new constitution's draft would force Mugabe to name a running mate, and would "greatly dilute his powers." Mugabe's inner circle is reportedly concerned that this new constitution will force them out of power, and that in naming a running mate, he would essentially be naming a successor.

Mugabe's party has also lost a significant amount of popularity in recent years. In the last elections in 2008, his party was narrowly defeated, and he only held on to his Presidency after signing a power-sharing deal with opposition leaders.

"As far as we're concerned, the constitution is a done deal," said Tendai Biti, head of the opposition party MDC, according to Bloomberg.

"We spent three years negotiating it with Zanu-PF and assumed, as anyone would, that their negotiators had the authority to negotiate. We don't see much reason to accept further delays."

Mugabe has been president of Zimbabwe since 1987.The referendum vote was originally scheduled for October, just before the new elections. It's unclear now when either of those votes will occur.