What is Marxist mass politics? I understand that the term "marxist regime" and derivatives were used in reference to peasant rebellions and movements and regimes that emerged from them i.e. Maoism or Latin American guerillas - but that is a misnomer. Marx did not envision a peasant rebellion in a backward society as a means to socialism. Socialism was supposed to develop from advanced industrial societies.
In many ways, his vision came true. For one thing, the mergence of the executive class - highly paid employees that took over the control of the firm putting owners (stockholders) to the back seat - or ESOP is consistent with Marx's prophecy of the producers taking the control of the means of production. It may lack the populist appeal and revolutionary romanticism - but it is a form of workers' control of the means of production nonetheless.
Or take the emergence of social welfare state in Europe that significantly improved the living conditions of the working class beyond anything that any other political system achieved. It may not abolished the sale of labour power but it significantly increased its "exchange value" i.e. social work needed to reproduce it from bare survival minimum to the highest standards of living known to humankind.
So Marxism, if taken literary is far from being dead - many of its predictions came true and today are taken for granted. Not a bad thing for a social scientist. What is dead is the era of peasant rebellions and their romanticized images in the West as populist revolutions bringing happiness and justice for all - a latter-days-collectivist Robin Hood if you will. Today's popular movement have the ugly face of the KKK, Posse Commitatus, angry white men, tax "relief" movements, Pol Pot, Taliban, Hamas etc.
Wojtek