Congo is heading to the polls to vote for president as authorities scramble to finalize preparations in an election facing steep logistical and security challenges. Some 44 million people, or almost half the population, are expected to vote. But many including several million displaced by conflict in the vast country’s east could struggle to cast their ballots. Experts and locals have warned that such challenges could affect the credibility of the vote in a country whose mineral resources are increasingly crucial to the global economy. One major concern is that ink on voting cards has smudged, making many illegible.