Bernie SandersBernie SandersThe Memo: Outrage rises among liberals over Israel On The Money: Biden says workers can't turn down job and get benefits | Treasury launches state and local aid | Businesses jump into vax push Symone Sanders 'hurt' at being passed over for press secretary: report MORE has opened up a 4-point lead over Democratic presidential rival Hillary ClintonHillary Diane Rodham ClintonAmerica departs Afghanistan as China arrives Young, diverse voters fueled Biden victory over Trump McConnell: Taliban could take over Afghanistan by 'the end of the year' MORE among voters in Wisconsin, according to a Marquette Law School poll released Wednesday afternoon.

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When asked to pick between Sanders, Clinton and someone else, 49.2 percent of likely Democratic primary voters opted for the Vermont senator, while 44.9 chose the former secretary of State.

None of the participants named a third candidate, but 5.5 percent said they have yet to make up their mind.

In the February version of the same poll, Sanders led Clinton 44 percent to 43 percent.

The April 5 Wisconsin primary, with its 96 delegates, is a must-win for Sanders, who is looking to hold on to the momentum he has been riding since sweeping all three Democratic elections on Saturday.

Sanders has won five of the last six contests, and a win in Wisconsin would further his argument that Clinton is a “weak front-runner” who remains vulnerable to defeat.

The poll surveyed 405 likely Democratic voters March 24–28. Its margin of error is 6.3 percentage points.