The Baader-Meinhof Gang (the popular name for the left-wing german terrorist group known as the Red Army Faction were definitely not a "Bonnie and Clyde" of their time. They were an extremely significant threat to the German state and at their height had as many as 70 active members.

Contemporary accounts in the American press would occasionally refer to Baader and Meinhof as "Bonnie Und Clyde"... one assumes in an attempt to be clever. But this presupposed that Baader and Meinhof were co-leaders of the group, as well as lovers. They were not. Andreas Baader was absolutely the leader of the organization, and his girlfriend Gudrun Ensslin was clearly the co-leader. Ulrike Meinhof, who was a secondary leader, had her name associated with Baader's because she was a famous journalist who helped lead a break of Baader from police custody. Because the group had not named themselves yet, the press dubbed them the Baader-Meinhof Group (or "gang" if it was a right-leaning news outlet).

In terms of popularity; this is a fascinating question. In the summer of 1971 the Allensbach Institute (a non-political organization that has surveyed the German public for more than half a century) conducted a survey that had a few questions about the public's attitude towards the Baader-Meinhof group.

The results, by most metrics, are simply astounding. I talk about the survey a bit in the introduction to my forthcoming book about the Baader-Meinhof Group:

It wasn’t just about killing Americans, and killing pigs, at least not at first. It was about attacking the illegitimate state that these pawns served. It was about scraping the bucolic soil and exposing the fascist, Nazi-tainted bedrock that the modern West German state was propped upon. It was about war on the forces of reaction. It was about Revolution.

The Baader-Meinhof Gang certainly didn’t expect to win their war by themselves. They assumed an epic proletarian backlash would be the Revolution’s true engine. They assumed their wave of terror would force the state to respond with brutal, reflexive anger. They assumed that West German civil liberties and civil rights would be quashed as the state turned the clock back 25 years to the Nazi era of open fascism. They assumed that the proletarian West Germans would react in horror as the true nature of their own government was revealed. They assumed that factory workers, bakers, and miners, would be inspired to smash their own oppressors. They assumed that they would be the vanguard of a movement where millions of Germans brought Revolution home. They assumed a lot.

It wasn’t complete conjecture. In July of 1971, Institut Allensbach, a public research firm with a standing and reputation similar to the Gallup organization in the United States, published a remarkable poll. Twenty percent of Germans under the age of thirty expressed “a certain sympathy” for the Baader-Meinhof Gang, a group with the avowed purpose of violently overthrowing the West German government. One in ten young Northern Germans indicated that they would willingly shelter a member of the Baader-Meinhof Gang for the night.

It was the last, and perhaps only, time that a significant portion of a western democracy expressed open support for terrorism as an avenue for Societal change.

For the leaders of the Baader-Meinhof Gang, this was empowering proof that millions of Germans were lining up behind their cause.

In retrospect, what is clear is that these millions of young middle-class Germans, primed by their radicalizing university experiences, were mostly expressing a theoretical support for a radical group that seemed to embody the realization of their leftists ideals. But save for killing a few policemen in shootouts, the Baader-Meinhof Gang hadn’t really begun their Revolution. There were no decapitated GIs yet, no maimed printing press operators. It was therefore easy to support them; they hadn’t yet truly turned their theory into praxis. This would all change one year later.

One way to look at it is this: West Germany had a population of 60 million at the time, so this survey showed that 8 million Germans were either willing to provide aid to an organization who's stated goal was to bring down the state and bring about socialist revolution... or were willing to consider it.

A year after that survey was released the group finally launched their true campaign, with bombings of American bases, police stations, printing plants, and more. Baader fully expected his army of 8 million to rise up and start their own wars against the state; in fact he counted on it. He knew his organization wasn't even remotely large enough to bring down the German state; but if he could inspire those 8 million, then he would be the vanguard of a revolution.

Of course it didn't work out that way. After the group bombed American bases, police stations, printing plants and more, killing many, that support evaporated instantly.

Virtually no one would express public support for the group. After the capture of the group, and the extreme response by the German state, many of their former supporters morphed their support into expressing outrage over the often horrible treatment of the imprisoned leaders.

I focus on this issue on one of my podcasts; it's worth a listen: http://www.baader-meinhof.com/podcast-35-popular-terrorists-anyway/

If you or anyone is interested in seeing the exact results published by the Allensbach Institute let me know and I'll post them on my site.