def mv_from_common_values_2(col_mvs, score=1):
    """
    Return mv candidates for missing values that are already candidates in 
    at least two columns.    
    """
    # Make dict with key: mv_candidate value: list of columns where applicable
    val_mvs = dict()
    for col, tuples in col_mvs.items():
        for (val, score, origin) in tuples:
            if val not in val_mvs:
                val_mvs[val] = [col]
            else:
                val_mvs[val].append(col)
                
    return [(val, score, 'common_values') for val, cols in val_mvs.items() if (len(cols)>=2)]