Graphs without spanning closed trails

Jaeger [J. Graph Theory 3 (1979) 91-93] proved that if a graph has two edge-disjoint spanning trees, then it is supereulerian, i.e., that it has a spanning closed trail. Catlin [J. Graph Theory 12 (1988) 29-45] showed that if G is one edge short of having two edge-disjoint spanning trees, then G has a cut edge or G is supereulerian. Catlin conjectured that if a connected graph G is at most two edges short of having two edge-disjoint spanning trees, then either G is supereulerian or G can be contracted to a K2 or a K2,t for some odd integer t ≥ 1. We prove Catlin’s conjecture in a more general context. Applications to spanning trails are discussed.