With one year to go until Election Day and 94 days until the Iowa caucuses, polling by Emerson College has provided snapshots of three battleground states critical not only to the leading candidates seeking the Democratic presidential nomination but to their potential general election matchups with President Trump.

Joe Biden leads in each state, though his advantage in one of them has diminished against his primary competitors.

There is good news for Biden in Nevada, however. The former vice president polls at 30% support, followed by Sen. Elizabeth Warren at 22% and Sen. Bernie Sanders at 19%. Though the front-runner has slipped somewhat in national polls, he has extended his lead by four percentage points since March, the last time Emerson polled in Nevada. The findings also offer good news for Warren, who has increased her support by 12 points since then.

Nevada is of particular importance as the third voting state in the primary. If Biden does not do well in either Iowa or New Hampshire, the Silver State could provide him with something of a bulwark.

“It is important for Biden to maintain his support in Nevada since polling shows him with some trouble in Iowa and New Hampshire,” noted Spencer Kimball, the director of Emerson Polling. “…Biden needs a firewall there or in South Carolina if he struggles in the first two contests in order to propel him on to Super Tuesday on March 3.”

Next up, on March 10, is Michigan, where Biden is ahead with 34% over Sanders at 28% -- but the leader has dropped from 40% while Sanders has gained five points since March. The Democratic socialist campaigned Sunday night in Detroit with Michigan Rep. Rashida Tlaib and was joined on stage by hometown son Jack White, the onetime frontman of the White Stripes.

Arizona will vote the same day (March 17) as Illinois and Florida. And Biden has reason for optimism in the Southwest: He leads with 28%, followed by Warren and Sanders, both polling at 21%.

The Biden campaign has been running on a political mix of nostalgia -- he was the vice president for the last Democrat to sit in the Oval Office -- and electability, as surveys and conventional wisdom hold that he has the best chance among Democrats to defeat Donald Trump. But voters in the three polled states indicated they do not want to go back in time, at least as measured by sentiments toward former Secretary of State Hillary Clinton, whose name has emerged of late as a possible late entry in the race.

Nevada respondents said no to the idea of Clinton running again, 67% to 23%.

Michigan voters also passed on a repeat, by a margin of 70 to 18%.

As for one-on-one matchups with the president, the Emerson snapshot shows Biden and Warren both at 50%-50% with Trump in Arizona, while Sanders trails by two points, 51-49%.

But in Michigan, Sanders leads Trump by sizable margin, 57%-43%; Biden tops Trump, 56%-44%, and Warren also leads the president, 54%-46%.

In Nevada, Trump and Sanders are tied at 50% support, while the president leads in matchups against Biden and Warren by the same narrow margin: 51%-49%.

The Nevada survey of 1,089 registered voters, conducted Oct. 31-Nov. 2, has a margin of error or plus or minus 2.9 percentage points. The Arizona survey of 901 registered voters, conducted Oct. 25-28, has a margin of error of plus or minus 3.2 percentage points. The Michigan survey of 1,051 registered voters, conducted Oct. 31-Nov.3, has a margin of error of plus or minus 3.0 percentage points.