BUCHAREST, Romania — For the second time in less than seven months, Romania is without a prime minister, after the governing Social Democrat Party pulled its support for the incumbent, forcing his resignation.

The prime minister, Mihai Tudose, announced on Monday evening that he would step down after party leaders failed to resolve a dispute between him and the party’s powerful leader, Liviu Dragnea, who is unable to serve as prime minister himself because of a 2016 conviction for electoral fraud.

Tensions had flared in recent weeks after Mr. Tudose tried to remove a close ally of Mr. Dragnea’s from her role as interior minister, after accusing her of lying to him.

The Social Democrats won a strong mandate in Romania’s last parliamentary elections, held in December 2016. But since then the country has been rocked by the largest protests in a quarter of a century, when hundreds of thousands of people took to the streets last February to oppose government measures that would have relaxed penalties for official corruption. The government backed down, but it has continued to push for similar measures, drawing protesters back into the streets, albeit in smaller numbers.