A method of nucleating a propylene homo- or copolymer, the method comprising contacting the propylene polymer with a semi-crystalline branched or coupled polymeric nucleating agent under nucleation conditions. In one embodiment, the propylene homopolymer is characterized as having .sup.13C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity. In another embodiment, the copolymer is characterized as comprising at least about 60 weight percent (wt %) of units derived from propylene, and as having at least one of the following properties: (i) .sup.13C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity, (ii) a B-value greater than about 1.4 when the comonomer content, i.e., the units derived from ethylene and/or the unsaturated comonomer(s), of the copolymer is at least about 3 wt %, (iii) a skewness index, S.sub.ix, greater than about -1.20, (iv) a DSC curve with a T.sub.me that remains essentially the same and a T.sub.max that decreases as the amount of comonomer, i.e., the units derived from ethylene and/or the unsaturated comonomer(s), in the copolymer is increased, and (v) an X-ray diffraction pattern that reports more gamma-form crystals than a comparable copolymer prepared with a Ziegler-Natta (Z-N) catalyst.