Donald Trump remains the national frontrunner ahead of the Wisconsin primary, but his support among Republicans and Republican-leaners has dropped three points to 45 percent, down from 48 percent last week.

Ted Cruz is behind him with 28 percent support and John Kasich has 18 percent support, according to the NBC News|SurveyMonkey Weekly Election Tracking poll conducted online from March 28 to April 3 of 14,071 adults aged 18 and over, including 12,116 registered voters.

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While Trump is still far ahead of the other candidates, this week’s 17-point margin is the lowest between Trump and Cruz since mid-February.

For Trump, it was a contentious news week. His campaign manager, Corey Lewandowski, was charged with assaulting a reporter. Trump also told MSNBC’s Chris Matthews that if abortions were illegal, women who have them should face “some form of punishment.” His campaign later released a statement clarifying the remark.

Related: Who Is Donald Trump's Controversial Top Aide

Even during a controversial week, Trump’s national numbers only slightly dipped from last week. Perhaps surprisingly, his support among women barely dropped from last week. Forty-two percent of women support Trump this week compared to 45 percent last week. Whether Trump’s numbers continue to slip this week will be of interest to those following the Republican contest closely.

While Trump’s national numbers remain strong, results from our poll suggest he may not get the support from a key demographic group in Wisconsin. In the weeks leading up to the Republican primary, conservative activists across Wisconsin have been advocating against Trump.

In 2008, 27 percent of Wisconsin Republican primary voters identified as very conservative and in 2012, that number grew to 32 percent; very conservative Republican primary voters are likely to be influential in today’s primary contest. Cruz continues to outperform Trump among registered voters who identify as very conservative in our tracking poll. Forty-five percent of that group support Cruz compared to 41 percent who support Trump.

Trump’s support among those who identify as conservative fell slightly from last week whereas Cruz’s support among that group rose slightly. Among registered voters who identify as conservative, Trump has 46 percent support — down 4 points from 50 percent support last week. Cruz has support from 28 percent of conservatives — up 2 points from 26 percent last week. In 2008 and 2012, 6 in 10 Wisconsin Republican primary voters identified as conservative.

All eyes will be on the Wisconsin Republican primary results tonight as the race heats up between Trump and Cruz. Although support among conservatives did not change significantly this week nationally, the question for the Republican race becomes is there a possibility of a continuing drop among this and other groups in the future?

The NBC News|SurveyMonkey Weekly Election Tracking poll was conducted online March 28 through April 3, 2016 among a national sample of 14,071 adults aged 18 and over, including 12,116 who say they are registered to vote. Respondents for this non-probability survey were selected from the nearly three million people who take surveys on the SurveyMonkey platform each day. Results have an error estimate of plus or minus 1.1 percentage points. For full results and methodology for this weekly tracking poll, please click here.