Bulgaria's main opposition Socialist Party (BSP) holds a narrow lead ahead of the governing centre-right GERB party, polls show less than a month before the European Parliament elections in the country of all Bulgarians who are certain how they will vote on May 26. Some 32.7% said they will support BSP, while 32.2% intend to back GERB, according to the results of a survey conducted by Sofia-based polling agency Alpha Research during April 20-30 and published earlier this month.In the previous poll conducted by Alpha Research in March, GERB led by a similar thin margin ahead of BSP.The second biggest opposition party Movement for Rights and Freedoms (DPS) has attracted the support of 9.3% of all respondents in the latest survey. Nationalist party VMRO, which is part of United Patriots - the junior partner of GERB in the government coalition, ranked fourth with 6% support, overtaking right-wing Democratic Bulgaria since the previous survey in March.Some 32.9% of the respondents in the latest poll of Alpha Research said they will certainly vote in the May 26 elections for members of the European Parliament (MEPs), while 36.7% said they will not vote.