After NPR reported on a Department of Homeland Security tool to check the citizenship of registered voters, three U.S. senators are expressing concern about accuracy, transparency and privacy.

Underground trains are incredibly susceptible to flooding from climate-driven extreme rain and sea level rise. Cities around the world are racing to adapt their transit systems.

Congressional Republicans have become more aligned with President Trump since he first took office. That makes even a single vote against him a "moderate" stance, even for staunch conservatives.

After his split with President Trump, Elon Musk says he's forming a new political party, perhaps to compete for key congressional contests. It likely wouldn't be easy.