I claim the ornamental design for the portable campfire, as shown and described.
FIG. 1 is a perspective view of the portable campfire showing the new design;
FIG. 2 is a first side view thereof;
FIG. 3 is a second side view thereof, opposite the first side;
FIG. 4 is a third side view thereof;
FIG. 5 is a fourth side view thereof, opposite the third side;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a cross-sectional view thereof, taken along line 8-8 of FIG. 2.
The dash-dash broken lines depict portions of the portable campfire that form no part of the claim. The dash-dot-dash broken lines define a symbolic break, the appearance of any portion of the article between the break lines forms no part of the claimed design.