  The transition helicity amplitudes from the proton ground state to the
$P_{11}(1440)$ and $D_{13}(1520)$ excited states ($\gamma_{v}pN^*$
electrocouplings) were determined from the analysis of nine independent
one-fold differential $\pi^{+} \pi^{-} p$ electroproduction cross sections off
a proton target, taken with CLAS at photon virtualities 0.25\enskip {\rm
GeV$^{2}$} $<$ $Q^{2}$ $<$ 0.60 \enskip {\rm GeV$^{2}$}. The phenomenological
reaction model was employed for separation of the resonant and non-resonant
contributions to the final state. The $P_{11}(1440)$ and $D_{13}(1520)$
electrocouplings were obtained from the resonant amplitudes parametrized within
the framework of a unitarized Breit-Wigner ansatz. They are consistent with
results obtained in the previous CLAS analyses of the $\pi^+n$ and $\pi^0p$
channels. The successful description of a large body of data in dominant
meson-electroproduction channels off protons with the same $\gamma_{v}pN^*$
electrocouplings offers clear evidence for the reliable extraction of these
fundamental quantities from meson-electroproduction data. This analysis also
led to the determination of the long-awaited hadronic branching ratios for the
$D_{13}(1520)$ decay into $\Delta\pi$ (24%-32%) and $N\rho$ (8%-17%).
