Two national polls found her lead over Sanders is narrowing.
But the pollster warned that Trump's support has slipped in recent days.
Poll comes as Trump drops plans to attend CPAC to campaign in Kansas.
The Texas senator is ahead of Trump by 9 points ahead of Super Tuesday.
Illinois poll shows Clinton with 51 percent support in Illinois.
A new poll shows Bernie Sanders ahead of Hillary Clinton in West Virginia.
Poll shows Trump in lead in Massachusetts, with Sanders and Clinton tied.
Clinton's lead is down from 25 points in January to 11 in a new NBC/WSJ poll.
The aide is downplaying a Wall Street Journal poll that puts Ted Cruz in the lead.
The Bloomberg poll shows Rubio and Bush in a tight race for third place.