Al Franken Smiles and Poses for Photo with Students Amid Harassment Allegations

Al Franken's still Mr. Popular in D.C. ... at least to a group of students eager to take a picture with the Senator.

We got Sen. Franken on Capitol Hill Tuesday looking to be in good spirits as he posed for a photo with some happy students from Virginia. His smile faded away, though, as we tried to ask him questions about allegations against him ... and got rebuffed by one of his aides.

As we've reported ... 3 women have accused Franken of groping their butts during photo ops, which led Marco Rubio to dish out some advice on how to avoid that problem.

For the record, Franken was much less handsy in this photo op.