党的先进性 the (CPC) Party’s pioneering role; the (CPC) Party’s pioneering nature; the (CPC) Party’s progressive nature ; the Party's vanguard nature

保持党的先进性 to maintain the Party's advanced nature

党的先进性建设 the (CPC) Party’s pioneering/progressive nature construction

加强党的先进性建设 to strengthen the Party's advanced nature

党的先进性和纯洁性 the (CPC) Party’s progressive nature and its integrity; the (CPC) Party’s pioneering nature and purity

党的先进性建设长效机制 the mechanism with lasting effect for the construction of the advanced/pioneering/progressive nature of the CPC; the lasting system of the CPC advanced/pioneering/progressive nature