By Ercan Gurses
ANKARA (Reuters) - Turkey's nationalist opposition leader faced a growing challenge on Thursday after a veteran party member resigned from his parliamentary role, strengthening party dissidents who see his continued leadership as a block to their electoral support.
Party rebels blame slipping support for the Nationalist Movement Party (MHP) on Devlet Bahceli, 68, whom they see as a dour figure unable to tap into nationalist sentiments that have swollen the popularity of President Tayyip Erdogan.
His replacement, after two decades at the helm, by a more popular figure could delay plans by the ruling AK Party to procure stronger presidential powers for Erdogan. That would involve early elections providing AK with a bigger majority allowing it to quickly change the constitution.
Leading MHP figure Oktay Vural, hitherto an ally of Bahceli, announced on Wednesday he was resigning from his position as head of the party's parliamentary group and a source close to Vural said he may align himself with the party dissidents.
"Vural was uneasy with the situation into which the party had fallen. But he definitely will not leave the MHP," a source close to Vural told Reuters. "He may act in line with the (party) dissidents from now on."
At an MHP congress on Sunday, party dissidents took a step toward replacing Bahceli, who has said that congress was invalid. The two sides are now engaged in a battle over who will manage a further congress on July 10 to elect a new leader.
Six rebels are bidding to become leader, most prominently Meral Aksener, a 59-year-old woman seen by pollsters as capable of revitalizing the MHP and increasing its support.
The pressure for an extraordinary party congress began after the MHP's representation in parliament halved to 40 MPs in a November election. A recent survey put it on 12 pct of the vote, just above the threshold needed to be in parliament but polls show its support could rise to 20 percent under new leadership.
At the June 19 congress, a series of changes were made to party regulations, including removing an obstacle to electing a new leader at an extraordinary congress and making it more difficult to expel party members.
The rebels are now seeking official approval from election authorities in Ankara for those changes before next month's leadership election, which will be closely watched by Erdogan and the ruling AK Party he founded.
Erdogan says Turkey needs a strong executive presidency to help steer the country through its big security and economic challenges.
Critics say Erdogan is behaving in an increasingly authoritarian way, undermining Turkey's constitutional checks and balances and clamping down on media freedoms in the European Union candidate nation. Erdogan rejects the accusations.
(Writing by Daren Butler; Editing by David Dolan)