With Democratic heavyweight Hillary Clinton as the unquestioned frontrunner, Sen. Bernie Sanders, I-Vt., faces a tough race for his party's 2016 presidential nomination. But the Vermont senator -- who is thought to be one of the few able to mount a serious challenge to Clinton -- this week managed to both draw a huge crowd at a campaign rally and surprise with promising poll numbers in an early caucus state.

Sanders' appearance at the Veterans Memorial Coliseum in Madison, Wisconsin, attracted almost 10,000 supporters on Wednesday, CBS News noted. The significance of the event was not lost on the candidate, who remarked that "there are a lot of people here."

"Tonight, we have more people at any meeting for a candidate of president of the United States than any other candidate," the senator contended. "We believe that the time has come when people in Wisconsin, Vermont and all over this country create a political movement which says to the billionaire class, 'You can't have it all,'"

Sanders used his rally to criticize Wisconsin Gov. Scott Walker, who is expected to join the increasingly crowded field of Republican White House contenders. The 73 year old ripped Walker's connection to the wealthy Koch brothers, who have donated heavily to past GOP campaigns.

Walker, for his part, used the opportunity to take to social networks to "welcome" Sanders to his state. "We have one thing in common: neither of us wants another President Clinton," the governor wrote.

Meanwhile, Sanders received good news from neighboring Iowa, which traditionally holds the first-in-the-nation caucuses. The senator is gaining against Clinton and is now favored by 33 percent of Democrats in the Hawkeye State, Time said based on a new Quinnipiac poll.

Clinton came in at 52 percent, and the former first lady and secretary of state still enjoys far greater name recognition than her one-time Senate colleague, the magazine added.

Sander's success in Iowa is partially linked to the "Run Warren Run" campaign, which had encouraged Elizabeth Warren to join the 2016 White House race -- a move that the Massachusetts senator has repeatedly ruled out, but the campaign's field director, Blair Lawton, has since joined the Sanders team.