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).

NATIONAL POLL: Among Democratic primary voters nationwide, Sanders is leading in overall preference to be their nominee. https://t.co/I6v444cU2i pic.twitter.com/wK4KR3jQI3 — CBS News Poll (@CBSNewsPoll) February 23, 2020

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.

NATIONAL POLL: 50% of Dem primary voters rated Warren's debate performance as impressive, ahead of all the other candidates, with Sanders named by 42%. Bloomberg was at the bottom, with just 15% saying his performance impressed them. pic.twitter.com/ei58XxQlmN — CBS News Poll (@CBSNewsPoll) February 23, 2020

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