EAU CLAIRE, WISCONSIN, USA (REUTERS) - With Donald Trump leading the Republican pack going into Tuesday's presidential primary in Wisconsin, Democratic candidates Hillary Clinton and Bernie Sanders are tussling over who could best take him on in November's general election.

Speaking in Eau Claire on Saturday (April 2), Sanders said his lead over Trump is greater than Clinton's.

Sanders said: "Let me tell you that the last CNN poll had us 20 points ahead of Donald Trump."

Clinton also took aim at Trump -- as well as his main rival Ted Cruz, who's currently leading in Wisconsin polls. She said she could withstand any attacks from Republicans, whomever their nominee may be.

Clinton said: "They've been after me a really long time. And it drives them crazy, but I'm still standing."

A recent Marquette Law School Poll found Sanders slightly ahead of Clinton in Wisconsin, 49 to 45 per cent.