The longer it takes to dispose off Sanders, harder it will be for Democrats to take on Trump and Cruz

With Senator Bernie Sanders turning up the heat on her in the Democratic Party nomination race, Hillary Clinton, the front-runner, will have to step up her game to meet Sanders' challenge, analysts said.

Sanders trounced Clinton on Tuesday, 57 percent to 43 percent, in the primary held in the state of Wisconsin, riding a wave of public discontent with Washington's elite.

Sanders' surprising success has ratcheted up the pressure on Clinton, the former secretary of state. She is feeling the squeeze as Sanders continues to surprise analysts and pundits who had previously thought he would be a flash in the pan, Xinhua reported.

The two rivals have fought a war of words in recent days by accusing each other of being "not qualified" to be president.

Indeed, Sanders has proven himself adept at outlining the struggles of ordinary Americans who have been left behind by the still sluggish US economy since 2008, and has shown himself to be a new voice for Democratic voters who are fed up with the elite in Washington.

In so doing, Sanders' recent victories also underscore the growing rift in the Democratic party between the far left and the establishment, the former group being supporters of Sanders, a self-proclaimed Democratic socialist.

"Sanders' victory in Wisconsin will keep the progressive money flowing into his campaign and make it much more difficult for Clinton to close down the nominating process," Brookings Institution's senior fellow Darrell West said.

"There already has been a dramatic increase in sniping between the two Democrats, and their campaign dialogue is likely to become more contentious over the next few weeks," he said.

"This creates problems in terms of bringing the party together and having a united front in November," West said.

Indeed, analysts say it is highly unlikely that Sanders will grab the nomination. But the more time Clinton spends fighting Sanders, the longer she has to put off forming and executing a strategy to take on the Republican nominee.

"The longer it takes to dispose of Sanders, the harder it will be for Democrats to take on Trump and Cruz. She has to work on connecting with average voters and giving them a reason to support her nomination," West said of Republican front-runner Donald Trump and No. 2 Republican candidate Senator Ted Cruz.

Julian Zelizer, professor of history and public affairs at Princeton University, said that Sanders' latest wins in states including Wisconsin hurt Clinton in her fight to clinch the nomination.

"It hurts in that it continued to demonstrate how viable he is... Each loss exposes her vulnerabilities. It also simply energizes his supporters," Zelizer said.

The blow will especially sting in the sense that Clinton will now have to busy herself with the fight against Sanders, and will have to postpone till later her preparation for the coming battle for the White House against the Republican nominee.

"This is the most costly aspect of (Sanders') victories, assuming he does not win in the end. Money, energy, attention need to focus on him rather than starting to shape the fall campaign," Zelizer said.

"I don't think there will be any dramatic changes at the point (in Clinton's campaign). So rather than thinking of the change, she needs to figure out how the current strategy can be more effective," he added.

Clinton's next round will be fought in the states of New York and Pennsylvania. As the screws tighten on her campaign, Clinton will need to deliver.

"Her Wisconsin loss elevates the importance of New York and Pennsylvania for Clinton. She really has to do well in those places in order to stay on top of the delegate count," West said.

"She has to reassure grass roots elements within the party that she is up to the challenge of a general election and can attract the white, working class voters she needs in order to win," he said.

Indeed, in the general election, single women, African Americans and Hispanics will be in the tank for Clinton, but she will have to make more inroads into the white working class -- many of whom support Trump.

"Sanders' success demonstrates that many Democrats have not bought into Clinton and are holding back from her campaign," West said.