Sen. Bernie Sanders (I-Vt.) won Saturday's Nevada caucuses decisively, after winning the New Hampshire primary and essentially tying former Mayor Pete Buttigieg for first in Iowa. So Sanders is the Democratic frontrunner, and he also leads nationally in a new CBS News/YouGov poll released Sunday, drawing the support of 28 percent of Democratic primary voters. But Sen. Elizabeth Warren (D-Mass.) jumped to second place in the poll, at 19 percent followed by former Vice President Joe Biden (17 percent), former Mayor Mike Bloomberg (13 percent), and Buttigieg (10 percent).

Warren came in fourth place in the Nevada caucuses, but a large majority of Nevada Democrats cast their early ballots before Wednesday night's Democratic presidential debate, and half the respondents in the CBS poll — taken Feb. 20-22, between the debate and the caucuses — were most impressed with Warren's performance. Warren's campaign also reported raising $14 million between the New Hampshire primary and Saturday.

CBS News has Biden leading in the next primary, South Carolina, but the big test will be Super Tuesday, March 3. And only 42 percent of Democratic primary voters have definitely made up their minds about who they will vote for, the poll found. At the same time, 69 percent of Warren's supporters are enthusiast about her candidacy followed by Sanders (65 percent), Biden (53 percent), and Buttigieg (52 percent). Democratic voters pick Sanders (57 percent) and Warren (53 percent) as the candidates who will fight the most for people like them.

A majority of all surveyed voters told CBS News/YouGov that President Trump will definitely (31 percent) or probably (34 percent) win re-election, even though in hypothetical head-to-head matchups, Sanders, Biden, and Warren all narrowly beat Trump.

YouGov conducted the poll Feb. 20-22 among 10,000 registered voters, including 6,598 Democrats and Democratic-leaning independents likely to vote in the primary. The margin of error for the entire poll is ±1.2 percentage points and for the Democrats, ±1.7 points. Peter Weber

In a stunning victory, progressive activist Cori Bush defeated Rep. William Lacy Clay in Missouri's 1st Congressional District Democratic primary on Tuesday.

Clay has represented the district for the last 20 years, and before that, his father, William Lacy Clay Sr., held the seat for three decades. Bush ran against the incumbent in 2018, but lost by a 20-point margin. On Tuesday, with 100 percent of precincts reporting, Bush has 48.6 percent of the vote, compared to Clay with 45.5 percent.

Bush was endorsed by Sen. Bernie Sanders (I-Vt.), and is calling for universal health care, raising the minimum wage, and police reform. In a victory speech, Bush said Missouri's 1st Congressional District "has decided that an incremental approach isn't going to work any longer. We decided that we the people have the answers, and we will lead from the front lines." Catherine Garcia

Voters in Missouri on Tuesday approved a ballot measure expanding Medicaid to roughly 230,000 low-income residents.

With 99 percent of precincts reporting, 53 percent voted "yes" on the measure, while 47 percent voted "no." Missouri is the sixth red state to expand Medicaid, and the second to do so amid the coronavirus pandemic, after Oklahoma. The state is now reporting on average more than 1,200 daily new coronavirus cases, nearly three times more than a month ago, Politico reports.

Missouri has until July 1, 2021, to expand Medicaid under the Affordable Care Act. The measure amends the state's constitution, so lawmakers cannot add requirements to the program. Gov. Mike Parson (R) opposed the expansion, saying it was too expensive and the state doesn't have enough money to pay for it. The federal government gives states up to 90 percent of funding necessary for Medicaid expansion, an improvement over the 65 percent provided to Missouri now under its current program.

"Quite frankly, Missourians are sick and tired of not getting their fair share," Jack Cardetti, a spokesman for the ballot initiative's organizers, told Politico last week "They pay their taxes, they've seen now 37 other states use that money to expand access to health care. Meanwhile, our economy's clearly ailing here." Catherine Garcia

To raise money for cancer research, Andrew Walker and Jacob Adkins traded in their ice skates for rollerblades and hit the road.

Walker and Adkins are hockey players at the University of Massachusetts Boston. They wanted to do something during the pandemic to help others, and came up with a way to raise money and awareness for the American Cancer Society: the roommates would rollerblade from Boston to Mason, Michigan, a nearly 900-mile journey.

Cancer has affected both of them personally, with Adkins' mother in remission after being diagnosed with Hodgkin's lymphoma and Walker's grandfather dying of the disease. Adkins and Walker — who dubbed themselves the Men in Blades — completed their trek in 10 days, arriving in Mason late last month. They raised $28,100, a feat they are especially proud of since donations to so many charities are down because of the pandemic.

"This experience has humbled both of us and has made us just that much more grateful for the people around us and that much more loving," Adkins told WHDH. Catherine Garcia

Rep. Roger Marshall defeated former Kansas Secretary of State Kris Kobach in Tuesday's Kansas Republican Senate primary.

With 70 percent of precincts reporting, Marshall has 39 percent of the vote compared to Kobach with 26.4 percent. Bob Hamilton is in third place with 19 percent, followed by David Lindstrom with 6.9 percent.

Republicans had been worried about the very conservative Kobach winning the primary but not being able to clinch the general election; he lost the state's governor's race in 2018 to Democrat Laura Kelly. "You have sustained real-world trials and evidence and data that say that Kris Kobach is an extremely poor general election candidate who absolutely could be the first Republican to lose a Senate race in Kansas in over 80 years," GOP political operative David Kensinger told KPR.

State Sen. Barbara Bollier, a former Republican and retired anesthesiologist, won the Democratic primary, and will face off against Marshall in November. They are vying to win the seat being vacated by Sen. Pat Roberts (R), who is retiring. Catherine Garcia

The Aurora Police Department in Colorado is apologizing after a video was posted online showing officers with their guns drawn as five members of a Black family, including a 6-year-old girl, lie face down in a parking lot.

The department says the officers mistakenly thought the family was in a stolen car. The incident took place on Sunday, with Brittany Gilliam telling CBS Denver she was sitting in the car with her 6-year-old daughter, 12-year-old sister, 14-year-old niece, and 17-year-old niece when a police officer approached. "He proceeded to handcuff me and I saw him handcuff the kids, so I started getting angry, why are you handcuffing kids," she said. Video shows Gilliam, her sister, and her 17-year-old niece in handcuffs, with the entire family face down on the asphalt and one of the children screaming, "I want my mother!"

The police department said Gilliam's car had the same license plate number as a suspected stolen motorcycle they were looking for — except Gilliam's plate wasn't from the right state. This was considered a "high-risk stop," Interim Chief of Police Vanessa Wilson said in a statement, and protocol calls for officers "drawing their weapons and ordering all occupants to exit the car and lie prone on the ground."

Wilson said the department will now look into enacting new practices and training for high-risk stops, and while Gilliam, who plans on filing a federal lawsuit against the department for excessive force, wants to see "better protocol," she is mostly worried about her daughter, sister, and nieces. "Those kids are not okay," she said. "They're never going to be okay. That was a traumatic experience. Would your kids be okay after that? Having a gun pulled on them and laid on the ground. Especially a 6-year-old."

The Aurora Police Department is already under scrutiny following last year's officer-involved death of Elijah McClain, a 23-year-old unarmed Black man who was detained as he walked home from the store. He died after being placed in a chokehold and injected with ketamine. Catherine Garcia

Lebanese officials believe Tuesday's enormous explosion in Beirut's port was likely caused by 2,700 tons of ammonium nitrate stored in a warehouse, and Prime Minister Hassan Diab vowed that those "responsible for this catastrophe will pay the price."

The blast killed at least 78 people and injured nearly 4,000, Lebanon's health ministry said, with many people still missing. The explosion leveled buildings, flipped cars, and blew out windows, and was so strong that it registered as a 3.3 magnitude earthquake.

Beirut's hospitals, already under stress due to the coronavirus pandemic, are now overwhelmed by patients, and medical facilities are asking for blood donations and generators. The city's governor, Marwan Abboud, told reporters he has "never in my life seen damage this enormous ... this is a national catastrophe. This is a disaster for Lebanon."

Lebanon is experiencing high unemployment and poverty rates, and Diab has asked for international assistance. Several countries, including Egypt, Jordan, and the United Kingdom, have pledged to help, and so has Israel, a country with which Lebanon is still technically at war; the country said it offered the Lebanese government "via international intermediaries medical and humanitarian aid, as well as immediate emergency assistance." Catherine Garcia