PRESIDENTIAL RACE

ELKO, Nevada — Florida Sen. Marco Rubio amasses increasing support in his effort to establish himself as the main challenger to front-runner Donald Trump as Republican presidential candidates crisscross Nevada on the final day of campaigning ahead of the Western state's caucuses. 

PRESIDENTIAL RACE-NEVADA IMMIGRATION

GOP 2016-NEVADA-IMMIGRATION -- Just when Nevada's Republican Party thought it had covered over the GOP divide on immigration the party's presidential election is ripping off the bandage, raising the specter that, even in states with a solid consensus on the issue, Republicans will perennially be divided on it. 

PRESIDENTIAL RACE-TRUMP-RETWEETS

LAS VEGAS — Donald Trump has repeated inaccurate and racially charged crime statistics, reposted pledges of support from white supremacists and retweeted dubious questions about the citizenship of his presidential rivals to an online following of more than 6 million people on Twitter alone. His response when challenged? To dismiss it all as nothing more than harmless "retweets." 

UNITED STATES-CHINA

WASHINGTON — The top diplomats of the U.S. and China meet Tuesday in Washington at a fraught time in relations between the two world powers. It's been seven weeks since North Korea's conducted a nuclear test and they still haven't agreed on how to censure Pyongyang. Also, tensions are rising in the South China Sea after Beijing deployed anti-aircraft missiles on a disputed island. 

UNITED STATES-RUSSIA

WASHINGTON — The United States and Russia agree on a new cease-fire for Syria that will take effect Saturday, even as major questions over enforcing and responding to violations of the truce were left unresolved. Where in Syria the fighting must stop and where counterterrorism operations can continue also must still be addressed. 

KALAMAZOO SHOOTING

KALAMAZOO, Michigan — The Uber ride-hailing service acknowledges that it received complaints about erratic driving by the suspect in the random shootings that killed six people in Kalamazoo, and a prosecutor said the man admitted carrying out the attacks. 

UBER-SAFETY

DETROIT — Uber is once again facing tough questions about safety after one of its drivers was charged with murder. The fast-growing, San Francisco-based ride-hailing company defended its screening of drivers Monday, saying it couldn't have predicted that driver Jason Dalton would engage in the random shootings that left a half-dozen people dead in Kalamazoo Saturday night. Uber said its safety procedures are robust and don't need to change.