The government has been accused of seeking a pretext to delay the September 23 presidential election.
More than 1,500 PPM supporters lined up at the Hulhumalé central park.
The opposition suspects schemes to deprive voting rights of Maldivians who need to re-register.
The resort workers association questioned the workability of the proposed scheme.
The joint opposition candidate will jail allies involved in the 2012 transfer of power, he contended.
Hardliners support the incumbent while the religious conservative party backs the opposition.
The opposition is seeking probes into the misuse of state resources.
Yameen challenged the opposition candidate to answer to the alleged "betrayals" of the MDP government.
More than 12,800 have registered to vote outside their home constituency.
There are concerns about voter manipulation, transparency and confusion caused by the changes.
There has been anger over changes to how and where Maldivians can vote in September.
All uniformed and civilian staff will have to vote in jails or detention centres.
The first U-turn was on resort ballot boxes for local workers.
Gaining access to the Maldives has been tough for foreign media in the past two years.
There are more than 27,000 Maldivian resort workers.
Sanctions were a last resort and action must be taken quickly, said a former Brussels official.
It will now be easier for drug convicts to be pardoned.